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	$239.43	10.388%	$264.302	$264.30	$264.30	$264.30
Purchase #2	$210.69	8.278%	$228.1309	$228.13	$228.15	$228.10
Purchase #3	$225.43	8.830%	$245.3355	$245.34	$245.35	$245.30
Purchase #4	$52.54	10.218%	$57.9085	$57.91	$57.90	$57.90
Purchase #5	$89.81	10.804%	$99.5131	$99.51	$99.50	$99.50
Purchase #6	$13.59	5.638%	$14.3562	$14.36	$14.35	$14.40
Purchase #7	$99.98	6.175%	$106.1538	$106.15	$106.15	$106.20
7 purchase totals =	$931.47		$1,015.7000	$1,015.70	$1,015.70	$1,015.70