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	$158.37	7.172%	$169.7283	$169.73	$169.75	$169.70
Purchase #2	$114.65	7.303%	$123.0229	$123.02	$123.00	$123.00
Purchase #3	$82.37	3.249%	$85.0462	$85.05	$85.05	$85.00
Purchase #4	$157.80	9.482%	$172.7626	$172.76	$172.75	$172.80
Purchase #5	$44.38	4.417%	$46.3403	$46.34	$46.35	$46.30
Purchase #6	$181.33	8.411%	$196.5817	$196.58	$196.60	$196.60
Purchase #7	$18.51	3.155%	$19.094	$19.09	$19.10	$19.10
7 purchase totals =	$757.41		$812.5760	$812.57	$812.60	$812.50