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	$48.98	11.757%	$54.7386	$54.74	$54.75	$54.70
Purchase #2	$170.25	12.853%	$192.1322	$192.13	$192.15	$192.10
Purchase #3	$157.52	6.193%	$167.2752	$167.28	$167.30	$167.30
Purchase #4	$158.32	13.594%	$179.842	$179.84	$179.85	$179.80
Purchase #5	$172.70	7.598%	$185.8217	$185.82	$185.80	$185.80
Purchase #6	$29.42	6.519%	$31.3379	$31.34	$31.35	$31.30
Purchase #7	$211.61	12.767%	$238.6262	$238.63	$238.65	$238.60
7 purchase totals =	$948.80		$1,049.7738	$1,049.78	$1,049.85	$1,049.60