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	$60.80	8.374%	$65.8914	$65.89	$65.90	$65.90
Purchase #2	$77.33	6.622%	$82.4508	$82.45	$82.45	$82.50
Purchase #3	$55.90	10.163%	$61.5811	$61.58	$61.60	$61.60
Purchase #4	$78.71	9.290%	$86.0222	$86.02	$86.00	$86.00
Purchase #5	$7.50	12.780%	$8.4585	$8.46	$8.45	$8.50
Purchase #6	$33.29	6.858%	$35.573	$35.57	$35.55	$35.60
Purchase #7	$215.87	6.431%	$229.7526	$229.75	$229.75	$229.80
7 purchase totals =	$529.40		$569.7296	$569.72	$569.70	$569.90