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	$129.25	9.201%	$141.1423	$141.14	$141.15	$141.10
Purchase #2	$55.69	3.256%	$57.5033	$57.50	$57.50	$57.50
Purchase #3	$90.58	11.147%	$100.677	$100.68	$100.70	$100.70
Purchase #4	$113.95	12.562%	$128.2644	$128.26	$128.25	$128.30
Purchase #5	$215.45	7.745%	$232.1366	$232.14	$232.15	$232.10
Purchase #6	$202.62	4.405%	$211.5454	$211.55	$211.55	$211.50
Purchase #7	$198.69	13.475%	$225.4635	$225.46	$225.45	$225.50
7 purchase totals =	$1,006.23		$1,096.7325	$1,096.73	$1,096.75	$1,096.70