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	$90.30	7.175%	$96.779	$96.78	$96.80	$96.80
Purchase #2	$91.60	3.871%	$95.1458	$95.15	$95.15	$95.10
Purchase #3	$6.92	8.802%	$7.5291	$7.53	$7.55	$7.50
Purchase #4	$126.44	13.816%	$143.909	$143.91	$143.90	$143.90
Purchase #5	$35.37	8.544%	$38.392	$38.39	$38.40	$38.40
Purchase #6	$85.76	3.627%	$88.8705	$88.87	$88.85	$88.90
Purchase #7	$210.29	8.390%	$227.9333	$227.93	$227.95	$227.90
7 purchase totals =	$646.68		$698.5587	$698.56	$698.60	$698.50