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	$55.86	10.814%	$61.9007	$61.90	$61.90	$61.90
Purchase #2	$128.54	8.569%	$139.5546	$139.55	$139.55	$139.60
Purchase #3	$226.79	6.143%	$240.7217	$240.72	$240.70	$240.70
Purchase #4	$81.64	6.731%	$87.1352	$87.14	$87.15	$87.10
Purchase #5	$178.42	11.694%	$199.2844	$199.28	$199.30	$199.30
Purchase #6	$167.81	11.774%	$187.5679	$187.57	$187.55	$187.60
Purchase #7	$227.51	12.681%	$256.3605	$256.36	$256.35	$256.40
7 purchase totals =	$1,066.57		$1,172.5250	$1,172.52	$1,172.50	$1,172.60