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	$235.50	3.210%	$243.0596	$243.06	$243.05	$243.10
Purchase #2	$246.85	11.565%	$275.3982	$275.40	$275.40	$275.40
Purchase #3	$113.56	4.405%	$118.5623	$118.56	$118.55	$118.60
Purchase #4	$120.61	7.865%	$130.096	$130.10	$130.10	$130.10
Purchase #5	$140.75	10.229%	$155.1473	$155.15	$155.15	$155.10
Purchase #6	$70.74	11.579%	$78.931	$78.93	$78.95	$78.90
Purchase #7	$12.81	12.737%	$14.4416	$14.44	$14.45	$14.40
7 purchase totals =	$940.82		$1,015.6360	$1,015.64	$1,015.65	$1,015.60