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	$152.89	4.242%	$159.3756	$159.38	$159.40	$159.40
Purchase #2	$244.48	7.547%	$262.9309	$262.93	$262.95	$262.90
Purchase #3	$171.53	4.851%	$179.8509	$179.85	$179.85	$179.90
Purchase #4	$109.69	7.118%	$117.4977	$117.50	$117.50	$117.50
Purchase #5	$216.58	13.390%	$245.5801	$245.58	$245.60	$245.60
Purchase #6	$15.32	13.314%	$17.3597	$17.36	$17.35	$17.40
Purchase #7	$98.48	13.284%	$111.5621	$111.56	$111.55	$111.60
7 purchase totals =	$1,008.97		$1,094.1570	$1,094.16	$1,094.20	$1,094.30