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	$114.82	7.219%	$123.1089	$123.11	$123.10	$123.10
Purchase #2	$230.55	10.106%	$253.8494	$253.85	$253.85	$253.80
Purchase #3	$101.45	7.488%	$109.0466	$109.05	$109.05	$109.00
Purchase #4	$130.78	5.760%	$138.3129	$138.31	$138.30	$138.30
Purchase #5	$200.40	8.678%	$217.7907	$217.79	$217.80	$217.80
Purchase #6	$173.83	13.222%	$196.8138	$196.81	$196.80	$196.80
Purchase #7	$49.67	13.801%	$56.525	$56.53	$56.55	$56.50
7 purchase totals =	$1,001.50		$1,095.4473	$1,095.45	$1,095.45	$1,095.30