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	$65.95	13.753%	$75.0201	$75.02	$75.00	$75.00
Purchase #2	$187.66	4.857%	$196.7746	$196.77	$196.75	$196.80
Purchase #3	$246.86	13.364%	$279.8504	$279.85	$279.85	$279.90
Purchase #4	$175.86	13.369%	$199.3707	$199.37	$199.35	$199.40
Purchase #5	$249.87	4.803%	$261.8713	$261.87	$261.85	$261.90
Purchase #6	$42.33	9.169%	$46.2112	$46.21	$46.20	$46.20
Purchase #7	$36.80	7.147%	$39.4301	$39.43	$39.45	$39.40
7 purchase totals =	$1,005.33		$1,098.5284	$1,098.52	$1,098.45	$1,098.60