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	$222.45	8.715%	$241.8365	$241.84	$241.85	$241.80
Purchase #2	$211.83	7.385%	$227.4736	$227.47	$227.45	$227.50
Purchase #3	$146.28	10.530%	$161.6833	$161.68	$161.70	$161.70
Purchase #4	$153.50	11.636%	$171.3613	$171.36	$171.35	$171.40
Purchase #5	$42.97	6.647%	$45.8262	$45.83	$45.85	$45.80
Purchase #6	$142.27	11.338%	$158.4006	$158.40	$158.40	$158.40
Purchase #7	$25.44	9.764%	$27.924	$27.92	$27.90	$27.90
7 purchase totals =	$944.74		$1,034.5055	$1,034.50	$1,034.50	$1,034.50