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	$113.93	8.155%	$123.221	$123.22	$123.20	$123.20
Purchase #2	$42.63	7.454%	$45.8076	$45.81	$45.80	$45.80
Purchase #3	$243.95	6.196%	$259.0651	$259.07	$259.05	$259.10
Purchase #4	$173.88	9.191%	$189.8613	$189.86	$189.85	$189.90
Purchase #5	$55.90	3.281%	$57.7341	$57.73	$57.75	$57.70
Purchase #6	$31.30	4.816%	$32.8074	$32.81	$32.80	$32.80
Purchase #7	$133.67	13.306%	$151.4561	$151.46	$151.45	$151.50
7 purchase totals =	$795.26		$859.9526	$859.96	$859.90	$860.00