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	$44.38	5.861%	$46.9811	$46.98	$47.00	$47.00
Purchase #2	$90.56	12.482%	$101.8637	$101.86	$101.85	$101.90
Purchase #3	$75.90	8.308%	$82.2058	$82.21	$82.20	$82.20
Purchase #4	$245.37	10.302%	$270.648	$270.65	$270.65	$270.60
Purchase #5	$220.28	13.709%	$250.4782	$250.48	$250.50	$250.50
Purchase #6	$164.38	4.105%	$171.1278	$171.13	$171.15	$171.10
Purchase #7	$161.58	3.485%	$167.2111	$167.21	$167.20	$167.20
7 purchase totals =	$1,002.45		$1,090.5157	$1,090.52	$1,090.55	$1,090.50