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	$134.97	11.448%	$150.4214	$150.42	$150.40	$150.40
Purchase #2	$240.73	13.385%	$272.9517	$272.95	$272.95	$273.00
Purchase #3	$88.80	8.680%	$96.5078	$96.51	$96.50	$96.50
Purchase #4	$139.91	3.447%	$144.7327	$144.73	$144.75	$144.70
Purchase #5	$39.54	13.791%	$44.993	$44.99	$45.00	$45.00
Purchase #6	$108.29	3.102%	$111.6492	$111.65	$111.65	$111.60
Purchase #7	$152.33	6.436%	$162.134	$162.13	$162.15	$162.10
7 purchase totals =	$904.57		$983.3898	$983.38	$983.40	$983.30