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	$200.65	11.467%	$223.6585	$223.66	$223.65	$223.70
Purchase #2	$243.70	11.791%	$272.4347	$272.43	$272.45	$272.40
Purchase #3	$177.72	6.301%	$188.9181	$188.92	$188.90	$188.90
Purchase #4	$160.63	7.212%	$172.2146	$172.21	$172.20	$172.20
Purchase #5	$164.65	10.787%	$182.4108	$182.41	$182.40	$182.40
Purchase #6	$94.67	6.231%	$100.5689	$100.57	$100.55	$100.60
Purchase #7	$26.89	7.130%	$28.8073	$28.81	$28.80	$28.80
7 purchase totals =	$1,068.91		$1,169.0129	$1,169.01	$1,168.95	$1,169.00