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	$173.43	6.181%	$184.1497	$184.15	$184.15	$184.10
Purchase #2	$247.72	12.114%	$277.7288	$277.73	$277.75	$277.70
Purchase #3	$41.54	3.385%	$42.9461	$42.95	$42.95	$42.90
Purchase #4	$224.81	13.730%	$255.6764	$255.68	$255.70	$255.70
Purchase #5	$91.48	8.517%	$99.2714	$99.27	$99.25	$99.30
Purchase #6	$169.96	10.528%	$187.8534	$187.85	$187.85	$187.90
Purchase #7	$117.48	3.568%	$121.6717	$121.67	$121.65	$121.70
7 purchase totals =	$1,066.42		$1,169.2975	$1,169.30	$1,169.30	$1,169.30