Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$201.87	10.660%	$223.3893	$223.39	$223.40	$223.40
Purchase #2	$240.80	5.216%	$253.3601	$253.36	$253.35	$253.40
Purchase #3	$128.45	12.166%	$144.0772	$144.08	$144.10	$144.10
Purchase #4	$177.39	10.560%	$196.1224	$196.12	$196.10	$196.10
Purchase #5	$225.29	11.347%	$250.8537	$250.85	$250.85	$250.90
Purchase #6	$119.75	3.700%	$124.1808	$124.18	$124.20	$124.20
Purchase #7	$160.69	13.603%	$182.5487	$182.55	$182.55	$182.50
7 purchase totals =	$1,254.24		$1,374.5322	$1,374.53	$1,374.55	$1,374.60