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	$244.34	3.637%	$253.2266	$253.23	$253.25	$253.20
Purchase #2	$229.66	13.841%	$261.4472	$261.45	$261.45	$261.40
Purchase #3	$167.94	6.432%	$178.7419	$178.74	$178.75	$178.70
Purchase #4	$162.68	7.289%	$174.5377	$174.54	$174.55	$174.50
Purchase #5	$119.65	11.533%	$133.4492	$133.45	$133.45	$133.40
Purchase #6	$69.79	3.241%	$72.0519	$72.05	$72.05	$72.10
Purchase #7	$111.80	10.467%	$123.5021	$123.50	$123.50	$123.50
7 purchase totals =	$1,105.86		$1,196.9566	$1,196.96	$1,197.00	$1,196.80