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	$210.61	8.103%	$227.6757	$227.68	$227.70	$227.70
Purchase #2	$212.42	4.734%	$222.476	$222.48	$222.50	$222.50
Purchase #3	$40.75	5.500%	$42.9913	$42.99	$43.00	$43.00
Purchase #4	$109.47	12.502%	$123.1559	$123.16	$123.15	$123.20
Purchase #5	$16.63	8.479%	$18.0401	$18.04	$18.05	$18.00
Purchase #6	$78.70	11.849%	$88.0252	$88.03	$88.05	$88.00
Purchase #7	$124.52	5.278%	$131.0922	$131.09	$131.10	$131.10
7 purchase totals =	$793.10		$853.4564	$853.47	$853.55	$853.50