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	$157.37	11.303%	$175.1575	$175.16	$175.15	$175.20
Purchase #2	$61.53	5.506%	$64.9178	$64.92	$64.90	$64.90
Purchase #3	$183.58	8.686%	$199.5258	$199.53	$199.55	$199.50
Purchase #4	$117.57	8.723%	$127.8256	$127.83	$127.85	$127.80
Purchase #5	$47.53	13.493%	$53.9432	$53.94	$53.95	$53.90
Purchase #6	$247.89	6.719%	$264.5457	$264.55	$264.55	$264.50
Purchase #7	$38.55	3.431%	$39.8727	$39.87	$39.85	$39.90
7 purchase totals =	$854.02		$925.7883	$925.80	$925.80	$925.70