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	$180.48	6.711%	$192.592	$192.59	$192.60	$192.60
Purchase #2	$21.46	4.788%	$22.4875	$22.49	$22.50	$22.50
Purchase #3	$224.82	12.735%	$253.4508	$253.45	$253.45	$253.50
Purchase #4	$229.43	6.171%	$243.5881	$243.59	$243.60	$243.60
Purchase #5	$207.72	13.527%	$235.8183	$235.82	$235.80	$235.80
Purchase #6	$136.78	7.494%	$147.0303	$147.03	$147.05	$147.00
Purchase #7	$62.58	4.811%	$65.5907	$65.59	$65.60	$65.60
7 purchase totals =	$1,063.27		$1,160.5577	$1,160.56	$1,160.60	$1,160.60