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	$138.28	9.864%	$151.9199	$151.92	$151.90	$151.90
Purchase #2	$68.37	6.185%	$72.5987	$72.60	$72.60	$72.60
Purchase #3	$74.35	11.262%	$82.7233	$82.72	$82.70	$82.70
Purchase #4	$147.58	6.159%	$156.6695	$156.67	$156.65	$156.70
Purchase #5	$184.91	4.432%	$193.1052	$193.11	$193.10	$193.10
Purchase #6	$11.53	6.505%	$12.28	$12.28	$12.30	$12.30
Purchase #7	$78.30	6.266%	$83.2063	$83.21	$83.20	$83.20
7 purchase totals =	$703.32		$752.5029	$752.51	$752.45	$752.50