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	$118.74	6.839%	$126.8606	$126.86	$126.85	$126.90
Purchase #2	$210.36	11.214%	$233.9498	$233.95	$233.95	$233.90
Purchase #3	$42.27	3.330%	$43.6776	$43.68	$43.70	$43.70
Purchase #4	$185.60	3.578%	$192.2408	$192.24	$192.25	$192.20
Purchase #5	$108.79	13.774%	$123.7747	$123.77	$123.75	$123.80
Purchase #6	$128.58	12.532%	$144.6936	$144.69	$144.70	$144.70
Purchase #7	$6.59	11.549%	$7.3511	$7.35	$7.35	$7.40
7 purchase totals =	$800.93		$872.5482	$872.54	$872.55	$872.60