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	$133.35	11.330%	$148.4586	$148.46	$148.45	$148.50
Purchase #2	$121.86	7.224%	$130.6632	$130.66	$130.65	$130.70
Purchase #3	$85.34	5.830%	$90.3153	$90.32	$90.30	$90.30
Purchase #4	$190.42	6.393%	$202.5936	$202.59	$202.60	$202.60
Purchase #5	$67.77	5.526%	$71.515	$71.52	$71.50	$71.50
Purchase #6	$140.70	7.610%	$151.4073	$151.41	$151.40	$151.40
Purchase #7	$96.87	9.496%	$106.0688	$106.07	$106.05	$106.10
7 purchase totals =	$836.31		$901.0218	$901.03	$900.95	$901.10