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	$206.40	5.654%	$218.0699	$218.07	$218.05	$218.10
Purchase #2	$104.57	6.592%	$111.4633	$111.46	$111.45	$111.50
Purchase #3	$37.50	3.261%	$38.7229	$38.72	$38.70	$38.70
Purchase #4	$175.25	8.627%	$190.3688	$190.37	$190.35	$190.40
Purchase #5	$147.74	12.345%	$165.9785	$165.98	$166.00	$166.00
Purchase #6	$239.42	12.485%	$269.3116	$269.31	$269.30	$269.30
Purchase #7	$169.65	4.284%	$176.9178	$176.92	$176.90	$176.90
7 purchase totals =	$1,080.53		$1,170.8328	$1,170.83	$1,170.75	$1,170.90