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	$47.63	11.192%	$52.9607	$52.96	$52.95	$53.00
Purchase #2	$221.98	4.448%	$231.8537	$231.85	$231.85	$231.90
Purchase #3	$186.48	6.143%	$197.9355	$197.94	$197.95	$197.90
Purchase #4	$246.89	9.620%	$270.6408	$270.64	$270.65	$270.60
Purchase #5	$65.64	9.449%	$71.8423	$71.84	$71.85	$71.80
Purchase #6	$34.71	5.218%	$36.5212	$36.52	$36.50	$36.50
Purchase #7	$191.31	9.139%	$208.7938	$208.79	$208.80	$208.80
7 purchase totals =	$994.64		$1,070.5480	$1,070.54	$1,070.55	$1,070.50