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	$156.74	9.689%	$171.9265	$171.93	$171.95	$171.90
Purchase #2	$96.55	3.607%	$100.0326	$100.03	$100.05	$100.00
Purchase #3	$70.29	3.350%	$72.6447	$72.64	$72.65	$72.60
Purchase #4	$160.82	8.871%	$175.0863	$175.09	$175.10	$175.10
Purchase #5	$184.84	12.638%	$208.2001	$208.20	$208.20	$208.20
Purchase #6	$158.59	11.302%	$176.5138	$176.51	$176.50	$176.50
Purchase #7	$100.82	12.791%	$113.7159	$113.72	$113.70	$113.70
7 purchase totals =	$928.65		$1,018.1199	$1,018.12	$1,018.15	$1,018.00