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	$86.76	4.439%	$90.6113	$90.61	$90.60	$90.60
Purchase #2	$150.74	8.339%	$163.3102	$163.31	$163.30	$163.30
Purchase #3	$54.60	13.136%	$61.7723	$61.77	$61.75	$61.80
Purchase #4	$176.65	11.239%	$196.5037	$196.50	$196.50	$196.50
Purchase #5	$249.46	6.846%	$266.538	$266.54	$266.55	$266.50
Purchase #6	$246.92	3.166%	$254.7375	$254.74	$254.75	$254.70
Purchase #7	$210.29	7.236%	$225.5066	$225.51	$225.50	$225.50
7 purchase totals =	$1,175.42		$1,258.9796	$1,258.98	$1,258.95	$1,258.90