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	$156.88	10.569%	$173.4606	$173.46	$173.45	$173.50
Purchase #2	$94.31	6.720%	$100.6476	$100.65	$100.65	$100.60
Purchase #3	$113.40	4.481%	$118.4815	$118.48	$118.50	$118.50
Purchase #4	$55.76	8.627%	$60.5704	$60.57	$60.55	$60.60
Purchase #5	$53.51	7.703%	$57.6319	$57.63	$57.65	$57.60
Purchase #6	$69.66	3.346%	$71.9908	$71.99	$72.00	$72.00
Purchase #7	$88.29	12.811%	$99.6008	$99.60	$99.60	$99.60
7 purchase totals =	$631.81		$682.3836	$682.38	$682.40	$682.40