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	$106.41	4.674%	$111.3836	$111.38	$111.40	$111.40
Purchase #2	$46.75	10.216%	$51.526	$51.53	$51.55	$51.50
Purchase #3	$125.86	13.166%	$142.4307	$142.43	$142.45	$142.40
Purchase #4	$170.25	13.584%	$193.3768	$193.38	$193.40	$193.40
Purchase #5	$126.50	13.229%	$143.2347	$143.23	$143.25	$143.20
Purchase #6	$238.39	8.500%	$258.6532	$258.65	$258.65	$258.70
Purchase #7	$176.44	9.255%	$192.7695	$192.77	$192.75	$192.80
7 purchase totals =	$990.60		$1,093.3745	$1,093.37	$1,093.45	$1,093.40