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	$43.31	4.800%	$45.3889	$45.39	$45.40	$45.40
Purchase #2	$15.40	11.551%	$17.1789	$17.18	$17.20	$17.20
Purchase #3	$15.85	12.740%	$17.8693	$17.87	$17.85	$17.90
Purchase #4	$68.82	11.600%	$76.8031	$76.80	$76.80	$76.80
Purchase #5	$190.98	13.374%	$216.5217	$216.52	$216.50	$216.50
Purchase #6	$50.91	3.405%	$52.6435	$52.64	$52.65	$52.60
Purchase #7	$82.27	5.596%	$86.8738	$86.87	$86.85	$86.90
7 purchase totals =	$467.54		$513.2792	$513.27	$513.25	$513.30