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	$140.69	4.405%	$146.8874	$146.89	$146.90	$146.90
Purchase #2	$141.99	9.739%	$155.8184	$155.82	$155.80	$155.80
Purchase #3	$77.96	13.315%	$88.3404	$88.34	$88.35	$88.30
Purchase #4	$230.97	9.639%	$253.2332	$253.23	$253.25	$253.20
Purchase #5	$172.90	4.108%	$180.0027	$180.00	$180.00	$180.00
Purchase #6	$222.55	9.517%	$243.7301	$243.73	$243.75	$243.70
Purchase #7	$17.37	6.635%	$18.5225	$18.52	$18.50	$18.50
7 purchase totals =	$1,004.43		$1,086.5347	$1,086.53	$1,086.55	$1,086.40