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	$147.57	13.397%	$167.34	$167.34	$167.35	$167.30
Purchase #2	$50.84	13.599%	$57.7537	$57.75	$57.75	$57.80
Purchase #3	$135.72	9.147%	$148.1343	$148.13	$148.15	$148.10
Purchase #4	$10.93	12.844%	$12.3338	$12.33	$12.35	$12.30
Purchase #5	$124.65	4.550%	$130.3216	$130.32	$130.30	$130.30
Purchase #6	$90.36	10.334%	$99.6978	$99.70	$99.70	$99.70
Purchase #7	$18.41	13.762%	$20.9436	$20.94	$20.95	$20.90
7 purchase totals =	$578.48		$636.5248	$636.51	$636.55	$636.40