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	$137.41	7.322%	$147.4712	$147.47	$147.45	$147.50
Purchase #2	$75.44	11.276%	$83.9466	$83.95	$83.95	$83.90
Purchase #3	$230.30	11.441%	$256.6486	$256.65	$256.65	$256.60
Purchase #4	$147.30	7.656%	$158.5773	$158.58	$158.60	$158.60
Purchase #5	$51.92	11.339%	$57.8072	$57.81	$57.80	$57.80
Purchase #6	$142.89	6.385%	$152.0135	$152.01	$152.00	$152.00
Purchase #7	$149.36	11.292%	$166.2257	$166.23	$166.25	$166.20
7 purchase totals =	$934.62		$1,022.6901	$1,022.70	$1,022.70	$1,022.60