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	$190.68	4.827%	$199.8841	$199.88	$199.90	$199.90
Purchase #2	$83.92	7.633%	$90.3256	$90.33	$90.35	$90.30
Purchase #3	$69.48	13.325%	$78.7382	$78.74	$78.75	$78.70
Purchase #4	$95.82	5.632%	$101.2166	$101.22	$101.20	$101.20
Purchase #5	$149.45	7.221%	$160.2418	$160.24	$160.25	$160.20
Purchase #6	$43.96	6.699%	$46.9049	$46.90	$46.90	$46.90
Purchase #7	$170.79	8.355%	$185.0595	$185.06	$185.05	$185.10
7 purchase totals =	$804.10		$862.3707	$862.37	$862.40	$862.30