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	$163.53	6.174%	$173.6263	$173.63	$173.65	$173.60
Purchase #2	$94.69	10.648%	$104.7726	$104.77	$104.75	$104.80
Purchase #3	$17.88	3.361%	$18.4809	$18.48	$18.50	$18.50
Purchase #4	$40.32	12.271%	$45.2677	$45.27	$45.25	$45.30
Purchase #5	$63.58	6.469%	$67.693	$67.69	$67.70	$67.70
Purchase #6	$170.33	6.515%	$181.427	$181.43	$181.45	$181.40
Purchase #7	$172.57	5.237%	$181.6075	$181.61	$181.60	$181.60
7 purchase totals =	$722.90		$772.8750	$772.88	$772.90	$772.90