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	$111.94	9.476%	$122.5474	$122.55	$122.55	$122.50
Purchase #2	$118.61	12.689%	$133.6604	$133.66	$133.65	$133.70
Purchase #3	$103.85	7.466%	$111.6034	$111.60	$111.60	$111.60
Purchase #4	$208.89	6.496%	$222.4595	$222.46	$222.45	$222.50
Purchase #5	$166.46	5.154%	$175.0393	$175.04	$175.05	$175.00
Purchase #6	$118.67	8.648%	$128.9326	$128.93	$128.95	$128.90
Purchase #7	$185.91	6.559%	$198.1038	$198.10	$198.10	$198.10
7 purchase totals =	$1,014.33		$1,092.3464	$1,092.34	$1,092.35	$1,092.30