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	$210.67	3.140%	$217.285	$217.29	$217.30	$217.30
Purchase #2	$192.65	12.194%	$216.1417	$216.14	$216.15	$216.10
Purchase #3	$183.55	4.555%	$191.9107	$191.91	$191.90	$191.90
Purchase #4	$43.55	8.506%	$47.2544	$47.25	$47.25	$47.30
Purchase #5	$119.92	8.250%	$129.8134	$129.81	$129.80	$129.80
Purchase #6	$35.86	4.665%	$37.5329	$37.53	$37.55	$37.50
Purchase #7	$27.82	13.562%	$31.5929	$31.59	$31.60	$31.60
7 purchase totals =	$814.02		$871.5310	$871.52	$871.55	$871.50