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	$167.67	10.840%	$185.8454	$185.85	$185.85	$185.80
Purchase #2	$98.30	13.118%	$111.195	$111.20	$111.20	$111.20
Purchase #3	$34.82	8.198%	$37.6745	$37.67	$37.65	$37.70
Purchase #4	$248.95	9.450%	$272.4758	$272.48	$272.50	$272.50
Purchase #5	$129.45	9.356%	$141.5613	$141.56	$141.55	$141.60
Purchase #6	$108.63	4.800%	$113.8442	$113.84	$113.85	$113.80
Purchase #7	$49.42	11.742%	$55.2229	$55.22	$55.20	$55.20
7 purchase totals =	$837.24		$917.8191	$917.82	$917.80	$917.80