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	$228.48	12.382%	$256.7704	$256.77	$256.75	$256.80
Purchase #2	$32.64	13.807%	$37.1466	$37.15	$37.15	$37.10
Purchase #3	$171.72	7.794%	$185.1039	$185.10	$185.10	$185.10
Purchase #4	$58.68	13.646%	$66.6875	$66.69	$66.70	$66.70
Purchase #5	$173.48	13.303%	$196.558	$196.56	$196.55	$196.60
Purchase #6	$240.28	11.585%	$268.1164	$268.12	$268.10	$268.10
Purchase #7	$236.69	3.312%	$244.5292	$244.53	$244.55	$244.50
7 purchase totals =	$1,141.97		$1,254.9120	$1,254.92	$1,254.90	$1,254.90