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	$49.35	11.294%	$54.9236	$54.92	$54.90	$54.90
Purchase #2	$134.26	13.107%	$151.8575	$151.86	$151.85	$151.90
Purchase #3	$147.95	9.561%	$162.0955	$162.10	$162.10	$162.10
Purchase #4	$217.95	11.282%	$242.5391	$242.54	$242.55	$242.50
Purchase #5	$228.73	6.209%	$242.9318	$242.93	$242.95	$242.90
Purchase #6	$129.58	9.125%	$141.4042	$141.40	$141.40	$141.40
Purchase #7	$56.81	7.653%	$61.1577	$61.16	$61.15	$61.20
7 purchase totals =	$964.63		$1,056.9094	$1,056.91	$1,056.90	$1,056.90