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	$82.42	4.541%	$86.1627	$86.16	$86.15	$86.20
Purchase #2	$114.80	13.572%	$130.3807	$130.38	$130.40	$130.40
Purchase #3	$52.79	12.851%	$59.574	$59.57	$59.55	$59.60
Purchase #4	$20.43	7.483%	$21.9588	$21.96	$21.95	$22.00
Purchase #5	$204.76	7.157%	$219.4147	$219.41	$219.40	$219.40
Purchase #6	$154.37	13.764%	$175.6175	$175.62	$175.60	$175.60
Purchase #7	$190.71	9.295%	$208.4365	$208.44	$208.45	$208.40
7 purchase totals =	$820.28		$901.5449	$901.54	$901.50	$901.60