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	$90.94	11.408%	$101.3144	$101.31	$101.30	$101.30
Purchase #2	$39.40	3.681%	$40.8503	$40.85	$40.85	$40.90
Purchase #3	$191.32	4.132%	$199.2253	$199.23	$199.25	$199.20
Purchase #4	$23.31	5.137%	$24.5074	$24.51	$24.50	$24.50
Purchase #5	$179.66	6.765%	$191.814	$191.81	$191.80	$191.80
Purchase #6	$132.62	4.426%	$138.4898	$138.49	$138.50	$138.50
Purchase #7	$10.30	8.291%	$11.154	$11.15	$11.15	$11.20
7 purchase totals =	$667.55		$707.3552	$707.35	$707.35	$707.40