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	$138.94	6.337%	$147.7446	$147.74	$147.75	$147.70
Purchase #2	$134.58	8.185%	$145.5954	$145.60	$145.60	$145.60
Purchase #3	$53.83	5.284%	$56.6744	$56.67	$56.65	$56.70
Purchase #4	$148.56	3.580%	$153.8784	$153.88	$153.90	$153.90
Purchase #5	$203.46	13.419%	$230.7623	$230.76	$230.75	$230.80
Purchase #6	$91.66	12.842%	$103.431	$103.43	$103.45	$103.40
Purchase #7	$213.56	4.162%	$222.4484	$222.45	$222.45	$222.40
7 purchase totals =	$984.59		$1,060.5345	$1,060.53	$1,060.55	$1,060.50