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	$233.79	11.113%	$259.7711	$259.77	$259.75	$259.80
Purchase #2	$59.29	3.337%	$61.2685	$61.27	$61.25	$61.30
Purchase #3	$135.54	6.838%	$144.8082	$144.81	$144.80	$144.80
Purchase #4	$50.77	12.487%	$57.1096	$57.11	$57.10	$57.10
Purchase #5	$14.57	13.195%	$16.4925	$16.49	$16.50	$16.50
Purchase #6	$160.34	5.263%	$168.7787	$168.78	$168.80	$168.80
Purchase #7	$118.48	4.463%	$123.7678	$123.77	$123.75	$123.80
7 purchase totals =	$772.78		$831.9964	$832.00	$831.95	$832.10