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	$182.38	4.335%	$190.2862	$190.29	$190.30	$190.30
Purchase #2	$182.97	7.394%	$196.4988	$196.50	$196.50	$196.50
Purchase #3	$115.88	11.222%	$128.8841	$128.88	$128.90	$128.90
Purchase #4	$133.99	3.821%	$139.1098	$139.11	$139.10	$139.10
Purchase #5	$97.72	5.775%	$103.3633	$103.36	$103.35	$103.40
Purchase #6	$169.86	3.165%	$175.2361	$175.24	$175.25	$175.20
Purchase #7	$130.62	13.110%	$147.7443	$147.74	$147.75	$147.70
7 purchase totals =	$1,013.42		$1,081.1226	$1,081.12	$1,081.15	$1,081.10