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	$46.57	4.623%	$48.7229	$48.72	$48.70	$48.70
Purchase #2	$79.35	9.168%	$86.6248	$86.62	$86.60	$86.60
Purchase #3	$18.54	10.667%	$20.5177	$20.52	$20.50	$20.50
Purchase #4	$33.94	10.106%	$37.37	$37.37	$37.35	$37.40
Purchase #5	$121.40	11.454%	$135.3052	$135.31	$135.30	$135.30
Purchase #6	$146.84	3.154%	$151.4713	$151.47	$151.45	$151.50
Purchase #7	$60.31	7.651%	$64.9243	$64.92	$64.90	$64.90
7 purchase totals =	$506.95		$544.9362	$544.93	$544.80	$544.90