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	$67.46	7.706%	$72.6585	$72.66	$72.65	$72.70
Purchase #2	$174.36	10.661%	$192.9485	$192.95	$192.95	$192.90
Purchase #3	$149.78	8.232%	$162.1099	$162.11	$162.10	$162.10
Purchase #4	$71.29	3.748%	$73.9619	$73.96	$73.95	$74.00
Purchase #5	$13.82	9.190%	$15.0901	$15.09	$15.10	$15.10
Purchase #6	$84.55	6.809%	$90.307	$90.31	$90.30	$90.30
Purchase #7	$160.43	11.268%	$178.5073	$178.51	$178.50	$178.50
7 purchase totals =	$721.69		$785.5832	$785.59	$785.55	$785.60