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	$149.39	13.489%	$169.5412	$169.54	$169.55	$169.50
Purchase #2	$168.25	9.639%	$184.4676	$184.47	$184.45	$184.50
Purchase #3	$203.32	12.735%	$229.2128	$229.21	$229.20	$229.20
Purchase #4	$118.69	8.490%	$128.7668	$128.77	$128.75	$128.80
Purchase #5	$234.96	7.121%	$251.6915	$251.69	$251.70	$251.70
Purchase #6	$93.91	6.655%	$100.1597	$100.16	$100.15	$100.20
Purchase #7	$112.42	5.459%	$118.557	$118.56	$118.55	$118.60
7 purchase totals =	$1,080.94		$1,182.3966	$1,182.40	$1,182.35	$1,182.50