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	$216.91	4.159%	$225.9313	$225.93	$225.95	$225.90
Purchase #2	$136.69	11.650%	$152.6144	$152.61	$152.60	$152.60
Purchase #3	$52.43	4.596%	$54.8397	$54.84	$54.85	$54.80
Purchase #4	$61.34	9.202%	$66.9845	$66.98	$67.00	$67.00
Purchase #5	$149.90	8.543%	$162.706	$162.71	$162.70	$162.70
Purchase #6	$192.56	5.867%	$203.8575	$203.86	$203.85	$203.90
Purchase #7	$32.54	3.486%	$33.6743	$33.67	$33.65	$33.70
7 purchase totals =	$842.37		$900.6077	$900.60	$900.60	$900.60