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	$50.95	5.121%	$53.5591	$53.56	$53.55	$53.60
Purchase #2	$193.51	12.231%	$217.1782	$217.18	$217.20	$217.20
Purchase #3	$53.83	6.841%	$57.5125	$57.51	$57.50	$57.50
Purchase #4	$64.37	12.334%	$72.3094	$72.31	$72.30	$72.30
Purchase #5	$19.46	12.331%	$21.8596	$21.86	$21.85	$21.90
Purchase #6	$205.70	7.242%	$220.5968	$220.60	$220.60	$220.60
Purchase #7	$69.38	12.714%	$78.201	$78.20	$78.20	$78.20
7 purchase totals =	$657.20		$721.2166	$721.22	$721.20	$721.30