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	$238.76	12.621%	$268.8939	$268.89	$268.90	$268.90
Purchase #2	$77.56	4.314%	$80.9059	$80.91	$80.90	$80.90
Purchase #3	$177.42	8.460%	$192.4297	$192.43	$192.45	$192.40
Purchase #4	$108.69	8.281%	$117.6906	$117.69	$117.70	$117.70
Purchase #5	$185.52	4.642%	$194.1318	$194.13	$194.15	$194.10
Purchase #6	$167.50	10.140%	$184.4845	$184.48	$184.50	$184.50
Purchase #7	$155.36	11.310%	$172.9312	$172.93	$172.95	$172.90
7 purchase totals =	$1,110.81		$1,211.4676	$1,211.46	$1,211.55	$1,211.40