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	$172.31	5.269%	$181.389	$181.39	$181.40	$181.40
Purchase #2	$182.39	7.725%	$196.4796	$196.48	$196.50	$196.50
Purchase #3	$92.89	7.214%	$99.5911	$99.59	$99.60	$99.60
Purchase #4	$13.40	5.646%	$14.1566	$14.16	$14.15	$14.20
Purchase #5	$26.77	3.371%	$27.6724	$27.67	$27.65	$27.70
Purchase #6	$32.91	13.502%	$37.3535	$37.35	$37.35	$37.40
Purchase #7	$206.49	12.756%	$232.8299	$232.83	$232.85	$232.80
7 purchase totals =	$727.16		$789.4721	$789.47	$789.50	$789.60