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	$248.56	6.659%	$265.1116	$265.11	$265.10	$265.10
Purchase #2	$100.83	5.454%	$106.3293	$106.33	$106.35	$106.30
Purchase #3	$149.49	13.389%	$169.5052	$169.51	$169.50	$169.50
Purchase #4	$80.94	11.189%	$89.9964	$90.00	$90.00	$90.00
Purchase #5	$190.78	12.237%	$214.1257	$214.13	$214.15	$214.10
Purchase #6	$6.72	10.855%	$7.4495	$7.45	$7.45	$7.40
Purchase #7	$248.42	4.613%	$259.8796	$259.88	$259.90	$259.90
7 purchase totals =	$1,025.74		$1,112.3973	$1,112.41	$1,112.45	$1,112.30