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	$36.28	3.246%	$37.4576	$37.46	$37.45	$37.50
Purchase #2	$243.76	13.840%	$277.4964	$277.50	$277.50	$277.50
Purchase #3	$246.48	12.286%	$276.7625	$276.76	$276.75	$276.80
Purchase #4	$32.36	6.254%	$34.3838	$34.38	$34.40	$34.40
Purchase #5	$147.48	11.434%	$164.3429	$164.34	$164.35	$164.30
Purchase #6	$106.65	4.720%	$111.6839	$111.68	$111.70	$111.70
Purchase #7	$153.95	5.406%	$162.2725	$162.27	$162.25	$162.30
7 purchase totals =	$966.96		$1,064.3996	$1,064.39	$1,064.40	$1,064.50