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	$125.96	3.679%	$130.5941	$130.59	$130.60	$130.60
Purchase #2	$203.66	12.578%	$229.2764	$229.28	$229.30	$229.30
Purchase #3	$143.72	11.132%	$159.7189	$159.72	$159.70	$159.70
Purchase #4	$123.34	3.285%	$127.3917	$127.39	$127.40	$127.40
Purchase #5	$199.71	3.592%	$206.8836	$206.88	$206.90	$206.90
Purchase #6	$105.78	9.313%	$115.6313	$115.63	$115.65	$115.60
Purchase #7	$162.38	11.594%	$181.2063	$181.21	$181.20	$181.20
7 purchase totals =	$1,064.55		$1,150.7023	$1,150.70	$1,150.75	$1,150.70