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	$141.66	7.404%	$152.1485	$152.15	$152.15	$152.10
Purchase #2	$160.70	7.835%	$173.2908	$173.29	$173.30	$173.30
Purchase #3	$175.57	5.806%	$185.7636	$185.76	$185.75	$185.80
Purchase #4	$137.41	3.158%	$141.7494	$141.75	$141.75	$141.70
Purchase #5	$114.33	5.640%	$120.7782	$120.78	$120.80	$120.80
Purchase #6	$199.82	5.175%	$210.1607	$210.16	$210.15	$210.20
Purchase #7	$214.61	8.747%	$233.3819	$233.38	$233.40	$233.40
7 purchase totals =	$1,144.10		$1,217.2731	$1,217.27	$1,217.30	$1,217.30