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	$33.53	10.664%	$37.1056	$37.11	$37.10	$37.10
Purchase #2	$226.83	10.353%	$250.3137	$250.31	$250.30	$250.30
Purchase #3	$30.73	13.537%	$34.8899	$34.89	$34.90	$34.90
Purchase #4	$170.80	7.772%	$184.0746	$184.07	$184.05	$184.10
Purchase #5	$234.43	11.155%	$260.5807	$260.58	$260.60	$260.60
Purchase #6	$174.53	6.261%	$185.4573	$185.46	$185.45	$185.50
Purchase #7	$213.98	10.494%	$236.4351	$236.44	$236.45	$236.40
7 purchase totals =	$1,084.83		$1,188.8569	$1,188.86	$1,188.85	$1,188.90