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	$187.40	9.662%	$205.5066	$205.51	$205.50	$205.50
Purchase #2	$225.75	13.556%	$256.3527	$256.35	$256.35	$256.40
Purchase #3	$173.45	11.508%	$193.4106	$193.41	$193.40	$193.40
Purchase #4	$34.29	4.654%	$35.8859	$35.89	$35.90	$35.90
Purchase #5	$153.94	13.867%	$175.2869	$175.29	$175.30	$175.30
Purchase #6	$220.34	4.334%	$229.8895	$229.89	$229.90	$229.90
Purchase #7	$99.27	12.308%	$111.4882	$111.49	$111.50	$111.50
7 purchase totals =	$1,094.44		$1,207.8204	$1,207.83	$1,207.85	$1,207.90