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	$244.80	8.588%	$265.8234	$265.82	$265.80	$265.80
Purchase #2	$73.90	4.118%	$76.9432	$76.94	$76.95	$76.90
Purchase #3	$7.50	5.435%	$7.9076	$7.91	$7.90	$7.90
Purchase #4	$103.77	5.552%	$109.5313	$109.53	$109.55	$109.50
Purchase #5	$153.60	7.563%	$165.2168	$165.22	$165.20	$165.20
Purchase #6	$223.75	6.872%	$239.1261	$239.13	$239.15	$239.10
Purchase #7	$229.69	9.672%	$251.9056	$251.91	$251.90	$251.90
7 purchase totals =	$1,037.01		$1,116.4540	$1,116.46	$1,116.45	$1,116.30