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	$132.32	9.212%	$144.5093	$144.51	$144.50	$144.50
Purchase #2	$25.46	13.738%	$28.9577	$28.96	$28.95	$29.00
Purchase #3	$18.31	12.315%	$20.5649	$20.56	$20.55	$20.60
Purchase #4	$221.28	5.801%	$234.1165	$234.12	$234.10	$234.10
Purchase #5	$182.90	7.754%	$197.0821	$197.08	$197.10	$197.10
Purchase #6	$72.53	7.757%	$78.1562	$78.16	$78.15	$78.20
Purchase #7	$230.69	10.528%	$254.977	$254.98	$255.00	$255.00
7 purchase totals =	$883.49		$958.3637	$958.37	$958.35	$958.50