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	$166.38	11.247%	$185.0928	$185.09	$185.10	$185.10
Purchase #2	$93.43	10.820%	$103.5391	$103.54	$103.55	$103.50
Purchase #3	$14.56	5.700%	$15.3899	$15.39	$15.40	$15.40
Purchase #4	$43.32	8.429%	$46.9714	$46.97	$46.95	$47.00
Purchase #5	$105.56	13.166%	$119.458	$119.46	$119.45	$119.50
Purchase #6	$29.29	12.136%	$32.8446	$32.84	$32.85	$32.80
Purchase #7	$235.29	6.283%	$250.0733	$250.07	$250.05	$250.10
7 purchase totals =	$687.83		$753.3691	$753.36	$753.35	$753.40