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	$71.45	4.500%	$74.6653	$74.67	$74.65	$74.70
Purchase #2	$58.51	11.370%	$65.1626	$65.16	$65.15	$65.20
Purchase #3	$212.61	3.203%	$219.4199	$219.42	$219.40	$219.40
Purchase #4	$217.88	9.390%	$238.3389	$238.34	$238.35	$238.30
Purchase #5	$189.65	13.787%	$215.797	$215.80	$215.80	$215.80
Purchase #6	$223.98	4.253%	$233.5059	$233.51	$233.50	$233.50
Purchase #7	$131.71	9.824%	$144.6492	$144.65	$144.65	$144.60
7 purchase totals =	$1,105.79		$1,191.5388	$1,191.55	$1,191.50	$1,191.50