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	$112.66	10.281%	$124.2426	$124.24	$124.25	$124.20
Purchase #2	$143.98	10.117%	$158.5465	$158.55	$158.55	$158.50
Purchase #3	$160.51	13.460%	$182.1146	$182.11	$182.10	$182.10
Purchase #4	$83.62	10.595%	$92.4795	$92.48	$92.50	$92.50
Purchase #5	$142.34	6.504%	$151.5978	$151.60	$151.60	$151.60
Purchase #6	$145.38	7.683%	$156.5495	$156.55	$156.55	$156.50
Purchase #7	$239.82	3.113%	$247.2856	$247.29	$247.30	$247.30
7 purchase totals =	$1,028.31		$1,112.8161	$1,112.82	$1,112.85	$1,112.70