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	$238.82	3.204%	$246.4718	$246.47	$246.45	$246.50
Purchase #2	$11.56	11.686%	$12.9109	$12.91	$12.90	$12.90
Purchase #3	$250.72	7.380%	$269.2231	$269.22	$269.20	$269.20
Purchase #4	$197.76	10.799%	$219.1161	$219.12	$219.10	$219.10
Purchase #5	$141.62	12.532%	$159.3678	$159.37	$159.35	$159.40
Purchase #6	$173.57	13.161%	$196.4135	$196.41	$196.40	$196.40
Purchase #7	$102.98	8.822%	$112.0649	$112.06	$112.05	$112.10
7 purchase totals =	$1,117.03		$1,215.5681	$1,215.56	$1,215.45	$1,215.60