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	$145.55	13.430%	$165.0974	$165.10	$165.10	$165.10
Purchase #2	$206.91	4.838%	$216.9203	$216.92	$216.90	$216.90
Purchase #3	$25.87	13.738%	$29.424	$29.42	$29.40	$29.40
Purchase #4	$64.71	12.116%	$72.5503	$72.55	$72.55	$72.60
Purchase #5	$246.66	4.720%	$258.3024	$258.30	$258.30	$258.30
Purchase #6	$57.54	6.553%	$61.3106	$61.31	$61.30	$61.30
Purchase #7	$123.43	5.364%	$130.0508	$130.05	$130.05	$130.10
7 purchase totals =	$870.67		$933.6558	$933.65	$933.60	$933.70