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	$181.59	5.142%	$190.9274	$190.93	$190.95	$190.90
Purchase #2	$55.67	9.651%	$61.0427	$61.04	$61.05	$61.00
Purchase #3	$176.53	13.711%	$200.734	$200.73	$200.75	$200.70
Purchase #4	$190.47	7.849%	$205.42	$205.42	$205.40	$205.40
Purchase #5	$195.71	4.861%	$205.2235	$205.22	$205.20	$205.20
Purchase #6	$229.43	6.245%	$243.7579	$243.76	$243.75	$243.80
Purchase #7	$188.51	6.402%	$200.5784	$200.58	$200.60	$200.60
7 purchase totals =	$1,217.91		$1,307.6839	$1,307.68	$1,307.70	$1,307.60