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	$231.78	13.679%	$263.4852	$263.49	$263.50	$263.50
Purchase #2	$113.27	12.556%	$127.4922	$127.49	$127.50	$127.50
Purchase #3	$237.30	11.548%	$264.7034	$264.70	$264.70	$264.70
Purchase #4	$38.29	7.850%	$41.2958	$41.30	$41.30	$41.30
Purchase #5	$108.89	4.393%	$113.6735	$113.67	$113.65	$113.70
Purchase #6	$85.44	4.575%	$89.3489	$89.35	$89.35	$89.30
Purchase #7	$166.35	11.236%	$185.0411	$185.04	$185.05	$185.00
7 purchase totals =	$981.32		$1,085.0401	$1,085.04	$1,085.05	$1,085.00