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	$201.82	13.825%	$229.7216	$229.72	$229.70	$229.70
Purchase #2	$186.30	7.547%	$200.3601	$200.36	$200.35	$200.40
Purchase #3	$50.87	13.768%	$57.8738	$57.87	$57.85	$57.90
Purchase #4	$98.71	13.384%	$111.9213	$111.92	$111.90	$111.90
Purchase #5	$171.88	9.382%	$188.0058	$188.01	$188.00	$188.00
Purchase #6	$76.84	8.655%	$83.4905	$83.49	$83.50	$83.50
Purchase #7	$110.69	12.507%	$124.534	$124.53	$124.55	$124.50
7 purchase totals =	$897.11		$995.9071	$995.90	$995.85	$995.90