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	$213.72	7.783%	$230.3538	$230.35	$230.35	$230.40
Purchase #2	$211.87	6.393%	$225.4148	$225.41	$225.40	$225.40
Purchase #3	$233.49	9.355%	$255.333	$255.33	$255.35	$255.30
Purchase #4	$43.83	7.461%	$47.1002	$47.10	$47.10	$47.10
Purchase #5	$206.87	7.754%	$222.9107	$222.91	$222.90	$222.90
Purchase #6	$33.65	5.637%	$35.5469	$35.55	$35.55	$35.50
Purchase #7	$213.95	8.366%	$231.8491	$231.85	$231.85	$231.80
7 purchase totals =	$1,157.38		$1,248.5085	$1,248.50	$1,248.50	$1,248.40