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	$212.84	9.256%	$232.5405	$232.54	$232.55	$232.50
Purchase #2	$93.75	5.391%	$98.8041	$98.80	$98.80	$98.80
Purchase #3	$31.87	4.619%	$33.3421	$33.34	$33.35	$33.30
Purchase #4	$83.88	11.486%	$93.5145	$93.51	$93.50	$93.50
Purchase #5	$67.78	6.656%	$72.2914	$72.29	$72.30	$72.30
Purchase #6	$40.63	9.607%	$44.5333	$44.53	$44.55	$44.50
Purchase #7	$154.67	7.397%	$166.1109	$166.11	$166.10	$166.10
7 purchase totals =	$685.42		$741.1368	$741.12	$741.15	$741.00