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	$246.74	11.439%	$274.9646	$274.96	$274.95	$275.00
Purchase #2	$225.98	4.140%	$235.3356	$235.34	$235.35	$235.30
Purchase #3	$89.62	13.238%	$101.4839	$101.48	$101.50	$101.50
Purchase #4	$156.98	4.871%	$164.6265	$164.63	$164.65	$164.60
Purchase #5	$110.36	12.529%	$124.187	$124.19	$124.20	$124.20
Purchase #6	$79.76	12.181%	$89.4756	$89.48	$89.50	$89.50
Purchase #7	$66.62	7.385%	$71.5399	$71.54	$71.55	$71.50
7 purchase totals =	$976.06		$1,061.6131	$1,061.62	$1,061.70	$1,061.60