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	$232.38	6.443%	$247.3522	$247.35	$247.35	$247.40
Purchase #2	$76.29	3.314%	$78.8183	$78.82	$78.80	$78.80
Purchase #3	$117.32	8.275%	$127.0282	$127.03	$127.05	$127.00
Purchase #4	$7.77	4.316%	$8.1054	$8.11	$8.10	$8.10
Purchase #5	$192.94	13.191%	$218.3907	$218.39	$218.40	$218.40
Purchase #6	$32.44	13.728%	$36.8934	$36.89	$36.90	$36.90
Purchase #7	$47.60	11.833%	$53.2325	$53.23	$53.25	$53.20
7 purchase totals =	$706.74		$769.8207	$769.82	$769.85	$769.80