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	11.164%	$200.84	$200.84	$200.85	$200.80
Purchase #2	$59.88	3.406%	$61.9195	$61.92	$61.90	$61.90
Purchase #3	$50.53	9.114%	$55.1353	$55.14	$55.15	$55.10
Purchase #4	$115.96	6.483%	$123.4777	$123.48	$123.50	$123.50
Purchase #5	$229.26	6.141%	$243.3389	$243.34	$243.35	$243.30
Purchase #6	$111.58	6.317%	$118.6285	$118.63	$118.65	$118.60
Purchase #7	$200.61	12.336%	$225.3572	$225.36	$225.35	$225.40
7 purchase totals =	$948.49		$1,028.6971	$1,028.71	$1,028.75	$1,028.60