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	$46.54	3.835%	$48.3248	$48.32	$48.30	$48.30
Purchase #2	$229.37	12.750%	$258.6147	$258.61	$258.60	$258.60
Purchase #3	$203.84	5.315%	$214.6741	$214.67	$214.65	$214.70
Purchase #4	$175.46	8.430%	$190.2513	$190.25	$190.25	$190.30
Purchase #5	$250.76	4.598%	$262.2899	$262.29	$262.30	$262.30
Purchase #6	$150.38	8.319%	$162.8901	$162.89	$162.90	$162.90
Purchase #7	$39.62	7.166%	$42.4592	$42.46	$42.45	$42.50
7 purchase totals =	$1,095.97		$1,179.5041	$1,179.49	$1,179.45	$1,179.60