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	$164.82	11.841%	$184.3363	$184.34	$184.35	$184.30
Purchase #2	$200.47	5.738%	$211.973	$211.97	$211.95	$212.00
Purchase #3	$89.81	10.642%	$99.3676	$99.37	$99.35	$99.40
Purchase #4	$209.96	8.440%	$227.6806	$227.68	$227.70	$227.70
Purchase #5	$162.26	12.619%	$182.7356	$182.74	$182.75	$182.70
Purchase #6	$137.37	3.243%	$141.8249	$141.82	$141.80	$141.80
Purchase #7	$187.37	11.319%	$208.5784	$208.58	$208.60	$208.60
7 purchase totals =	$1,152.06		$1,256.4964	$1,256.50	$1,256.50	$1,256.50