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	$92.96	5.135%	$97.7335	$97.73	$97.75	$97.70
Purchase #2	$89.90	11.747%	$100.4606	$100.46	$100.45	$100.50
Purchase #3	$85.49	13.672%	$97.1782	$97.18	$97.20	$97.20
Purchase #4	$86.75	10.563%	$95.9134	$95.91	$95.90	$95.90
Purchase #5	$243.31	8.269%	$263.4293	$263.43	$263.45	$263.40
Purchase #6	$20.51	9.208%	$22.3986	$22.40	$22.40	$22.40
Purchase #7	$172.53	13.789%	$196.3202	$196.32	$196.30	$196.30
7 purchase totals =	$791.45		$873.4338	$873.43	$873.45	$873.40