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	$42.56	3.410%	$44.0113	$44.01	$44.00	$44.00
Purchase #2	$96.56	12.516%	$108.6454	$108.65	$108.65	$108.60
Purchase #3	$208.73	8.168%	$225.7791	$225.78	$225.80	$225.80
Purchase #4	$140.73	4.142%	$146.559	$146.56	$146.55	$146.60
Purchase #5	$191.36	11.456%	$213.2822	$213.28	$213.30	$213.30
Purchase #6	$31.81	11.458%	$35.4548	$35.45	$35.45	$35.50
Purchase #7	$39.50	8.213%	$42.7441	$42.74	$42.75	$42.70
7 purchase totals =	$751.25		$816.4759	$816.47	$816.50	$816.50