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	$180.67	8.595%	$196.1986	$196.20	$196.20	$196.20
Purchase #2	$196.77	6.102%	$208.7769	$208.78	$208.80	$208.80
Purchase #3	$181.31	11.472%	$202.1099	$202.11	$202.10	$202.10
Purchase #4	$189.82	12.480%	$213.5095	$213.51	$213.50	$213.50
Purchase #5	$128.36	4.682%	$134.3698	$134.37	$134.35	$134.40
Purchase #6	$145.27	5.221%	$152.8545	$152.85	$152.85	$152.90
Purchase #7	$210.39	5.654%	$222.2855	$222.29	$222.30	$222.30
7 purchase totals =	$1,232.59		$1,330.1047	$1,330.11	$1,330.10	$1,330.20