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	$211.72	13.717%	$240.7616	$240.76	$240.75	$240.80
Purchase #2	$79.58	4.622%	$83.2582	$83.26	$83.25	$83.30
Purchase #3	$47.82	4.327%	$49.8892	$49.89	$49.90	$49.90
Purchase #4	$211.57	11.554%	$236.0148	$236.01	$236.00	$236.00
Purchase #5	$53.95	3.467%	$55.8204	$55.82	$55.80	$55.80
Purchase #6	$135.35	12.518%	$152.2931	$152.29	$152.30	$152.30
Purchase #7	$116.60	12.793%	$131.5166	$131.52	$131.50	$131.50
7 purchase totals =	$856.59		$949.5539	$949.55	$949.50	$949.60