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	$161.79	7.460%	$173.8595	$173.86	$173.85	$173.90
Purchase #2	$113.29	9.318%	$123.8464	$123.85	$123.85	$123.80
Purchase #3	$185.25	6.125%	$196.5966	$196.60	$196.60	$196.60
Purchase #4	$237.54	5.314%	$250.1629	$250.16	$250.15	$250.20
Purchase #5	$242.41	4.376%	$253.0179	$253.02	$253.00	$253.00
Purchase #6	$231.42	13.237%	$262.0531	$262.05	$262.05	$262.10
Purchase #7	$204.85	12.809%	$231.0892	$231.09	$231.10	$231.10
7 purchase totals =	$1,376.55		$1,490.6256	$1,490.63	$1,490.60	$1,490.70