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	$107.81	5.637%	$113.8872	$113.89	$113.90	$113.90
Purchase #2	$50.51	9.284%	$55.1993	$55.20	$55.20	$55.20
Purchase #3	$202.91	8.304%	$219.7596	$219.76	$219.75	$219.80
Purchase #4	$172.80	10.273%	$190.5517	$190.55	$190.55	$190.60
Purchase #5	$171.89	7.779%	$185.2613	$185.26	$185.25	$185.30
Purchase #6	$71.32	8.679%	$77.5099	$77.51	$77.50	$77.50
Purchase #7	$152.85	8.712%	$166.1663	$166.17	$166.15	$166.20
7 purchase totals =	$930.09		$1,008.3353	$1,008.34	$1,008.30	$1,008.50