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	$105.61	5.702%	$111.6319	$111.63	$111.65	$111.60
Purchase #2	$78.73	9.712%	$86.3763	$86.38	$86.40	$86.40
Purchase #3	$136.79	7.237%	$146.6895	$146.69	$146.70	$146.70
Purchase #4	$126.40	3.125%	$130.35	$130.35	$130.35	$130.40
Purchase #5	$200.89	10.356%	$221.6942	$221.69	$221.70	$221.70
Purchase #6	$165.88	8.143%	$179.3876	$179.39	$179.40	$179.40
Purchase #7	$246.32	7.638%	$265.1339	$265.13	$265.15	$265.10
7 purchase totals =	$1,060.62		$1,141.2634	$1,141.26	$1,141.35	$1,141.30