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	$21.31	11.323%	$23.7229	$23.72	$23.70	$23.70
Purchase #2	$168.98	3.499%	$174.8926	$174.89	$174.90	$174.90
Purchase #3	$174.55	9.230%	$190.661	$190.66	$190.65	$190.70
Purchase #4	$193.32	13.365%	$219.1572	$219.16	$219.15	$219.20
Purchase #5	$111.51	11.638%	$124.4875	$124.49	$124.50	$124.50
Purchase #6	$201.37	7.810%	$217.097	$217.10	$217.10	$217.10
Purchase #7	$104.35	11.247%	$116.0862	$116.09	$116.10	$116.10
7 purchase totals =	$975.39		$1,066.1044	$1,066.11	$1,066.10	$1,066.20