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	$241.88	5.117%	$254.257	$254.26	$254.25	$254.30
Purchase #2	$156.35	10.370%	$172.5635	$172.56	$172.55	$172.60
Purchase #3	$134.78	8.628%	$146.4088	$146.41	$146.40	$146.40
Purchase #4	$237.55	3.361%	$245.5341	$245.53	$245.55	$245.50
Purchase #5	$236.31	12.102%	$264.9082	$264.91	$264.90	$264.90
Purchase #6	$40.58	10.537%	$44.8559	$44.86	$44.85	$44.90
Purchase #7	$171.90	6.394%	$182.8913	$182.89	$182.90	$182.90
7 purchase totals =	$1,219.35		$1,311.4188	$1,311.42	$1,311.40	$1,311.50