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	$145.79	4.872%	$152.8929	$152.89	$152.90	$152.90
Purchase #2	$118.60	11.719%	$132.4987	$132.50	$132.50	$132.50
Purchase #3	$219.41	8.307%	$237.6364	$237.64	$237.65	$237.60
Purchase #4	$70.34	12.419%	$79.0755	$79.08	$79.10	$79.10
Purchase #5	$110.51	7.626%	$118.9375	$118.94	$118.95	$118.90
Purchase #6	$206.34	7.753%	$222.3375	$222.34	$222.35	$222.30
Purchase #7	$133.59	4.413%	$139.4853	$139.49	$139.50	$139.50
7 purchase totals =	$1,004.58		$1,082.8638	$1,082.88	$1,082.95	$1,082.80