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	$190.58	4.632%	$199.4077	$199.41	$199.40	$199.40
Purchase #2	$82.49	12.559%	$92.8499	$92.85	$92.85	$92.80
Purchase #3	$196.38	7.582%	$211.2695	$211.27	$211.25	$211.30
Purchase #4	$87.69	13.579%	$99.5974	$99.60	$99.60	$99.60
Purchase #5	$64.41	4.325%	$67.1957	$67.20	$67.20	$67.20
Purchase #6	$244.77	7.284%	$262.599	$262.60	$262.60	$262.60
Purchase #7	$93.68	4.252%	$97.6633	$97.66	$97.65	$97.70
7 purchase totals =	$960.00		$1,030.5825	$1,030.59	$1,030.55	$1,030.60