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	$129.25	3.254%	$133.4558	$133.46	$133.45	$133.50
Purchase #2	$57.64	7.287%	$61.8402	$61.84	$61.85	$61.80
Purchase #3	$120.33	11.788%	$134.5145	$134.51	$134.50	$134.50
Purchase #4	$128.52	9.399%	$140.5996	$140.60	$140.60	$140.60
Purchase #5	$40.61	9.158%	$44.3291	$44.33	$44.35	$44.30
Purchase #6	$75.69	4.182%	$78.8554	$78.86	$78.85	$78.90
Purchase #7	$17.47	8.630%	$18.9777	$18.98	$19.00	$19.00
7 purchase totals =	$569.51		$612.5723	$612.58	$612.60	$612.60