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	$59.26	10.559%	$65.5173	$65.52	$65.50	$65.50
Purchase #2	$200.88	13.573%	$228.1454	$228.15	$228.15	$228.10
Purchase #3	$167.58	13.775%	$190.6641	$190.66	$190.65	$190.70
Purchase #4	$34.31	10.597%	$37.9458	$37.95	$37.95	$37.90
Purchase #5	$76.97	13.699%	$87.5141	$87.51	$87.50	$87.50
Purchase #6	$89.80	7.253%	$96.3132	$96.31	$96.30	$96.30
Purchase #7	$70.46	11.517%	$78.5749	$78.57	$78.55	$78.60
7 purchase totals =	$699.26		$784.6748	$784.67	$784.60	$784.60