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	$48.73	7.504%	$52.3867	$52.39	$52.40	$52.40
Purchase #2	$155.27	8.433%	$168.3639	$168.36	$168.35	$168.40
Purchase #3	$111.98	12.146%	$125.5811	$125.58	$125.60	$125.60
Purchase #4	$181.47	7.269%	$194.6611	$194.66	$194.65	$194.70
Purchase #5	$47.53	4.618%	$49.7249	$49.72	$49.70	$49.70
Purchase #6	$83.27	7.145%	$89.2196	$89.22	$89.20	$89.20
Purchase #7	$220.90	9.375%	$241.6094	$241.61	$241.60	$241.60
7 purchase totals =	$849.15		$921.5467	$921.54	$921.50	$921.60