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	$216.39	12.230%	$242.8545	$242.85	$242.85	$242.90
Purchase #2	$244.86	4.578%	$256.0697	$256.07	$256.05	$256.10
Purchase #3	$224.98	12.555%	$253.2262	$253.23	$253.25	$253.20
Purchase #4	$5.35	5.711%	$5.6555	$5.66	$5.65	$5.70
Purchase #5	$142.29	10.311%	$156.9615	$156.96	$156.95	$157.00
Purchase #6	$100.27	10.804%	$111.1032	$111.10	$111.10	$111.10
Purchase #7	$241.41	12.213%	$270.8934	$270.89	$270.90	$270.90
7 purchase totals =	$1,175.55		$1,296.7640	$1,296.76	$1,296.75	$1,296.90