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	$164.67	12.805%	$185.756	$185.76	$185.75	$185.80
Purchase #2	$188.91	12.174%	$211.9079	$211.91	$211.90	$211.90
Purchase #3	$100.91	5.742%	$106.7043	$106.70	$106.70	$106.70
Purchase #4	$11.33	8.607%	$12.3052	$12.31	$12.30	$12.30
Purchase #5	$137.82	7.693%	$148.4225	$148.42	$148.40	$148.40
Purchase #6	$65.72	7.615%	$70.7246	$70.72	$70.70	$70.70
Purchase #7	$181.45	8.391%	$196.6755	$196.68	$196.70	$196.70
7 purchase totals =	$850.81		$932.4960	$932.50	$932.45	$932.50