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	$246.50	7.793%	$265.7097	$265.71	$265.70	$265.70
Purchase #2	$208.54	6.773%	$222.6644	$222.66	$222.65	$222.70
Purchase #3	$202.44	13.330%	$229.4253	$229.43	$229.45	$229.40
Purchase #4	$89.49	7.649%	$96.3351	$96.34	$96.35	$96.30
Purchase #5	$10.93	12.196%	$12.263	$12.26	$12.25	$12.30
Purchase #6	$124.72	9.183%	$136.173	$136.17	$136.15	$136.20
Purchase #7	$166.76	11.467%	$185.8824	$185.88	$185.90	$185.90
7 purchase totals =	$1,049.38		$1,148.4529	$1,148.45	$1,148.45	$1,148.50