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	$33.59	11.444%	$37.434	$37.43	$37.45	$37.40
Purchase #2	$107.70	3.699%	$111.6838	$111.68	$111.70	$111.70
Purchase #3	$233.91	3.527%	$242.16	$242.16	$242.15	$242.20
Purchase #4	$189.66	12.378%	$213.1361	$213.14	$213.15	$213.10
Purchase #5	$186.93	4.143%	$194.6745	$194.67	$194.65	$194.70
Purchase #6	$105.30	6.144%	$111.7696	$111.77	$111.75	$111.80
Purchase #7	$152.91	10.719%	$169.3004	$169.30	$169.30	$169.30
7 purchase totals =	$1,010.00		$1,080.1584	$1,080.15	$1,080.15	$1,080.20