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	$152.98	13.456%	$173.565	$173.57	$173.55	$173.60
Purchase #2	$58.88	12.607%	$66.303	$66.30	$66.30	$66.30
Purchase #3	$216.96	9.832%	$238.2915	$238.29	$238.30	$238.30
Purchase #4	$133.93	12.354%	$150.4757	$150.48	$150.50	$150.50
Purchase #5	$231.70	3.114%	$238.9151	$238.92	$238.90	$238.90
Purchase #6	$177.59	4.121%	$184.9085	$184.91	$184.90	$184.90
Purchase #7	$41.64	13.580%	$47.2947	$47.29	$47.30	$47.30
7 purchase totals =	$1,013.68		$1,099.7535	$1,099.76	$1,099.75	$1,099.80