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	$220.74	6.280%	$234.6025	$234.60	$234.60	$234.60
Purchase #2	$135.27	4.256%	$141.0271	$141.03	$141.05	$141.00
Purchase #3	$160.71	7.111%	$172.1381	$172.14	$172.15	$172.10
Purchase #4	$187.59	4.760%	$196.5193	$196.52	$196.50	$196.50
Purchase #5	$183.52	13.474%	$208.2475	$208.25	$208.25	$208.20
Purchase #6	$140.32	7.818%	$151.2902	$151.29	$151.30	$151.30
Purchase #7	$109.76	12.260%	$123.2166	$123.22	$123.20	$123.20
7 purchase totals =	$1,137.91		$1,227.0413	$1,227.05	$1,227.05	$1,226.90