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	$46.82	4.668%	$49.0056	$49.01	$49.00	$49.00
Purchase #2	$194.43	8.300%	$210.5677	$210.57	$210.55	$210.60
Purchase #3	$170.29	3.142%	$175.6405	$175.64	$175.65	$175.60
Purchase #4	$217.69	12.673%	$245.2779	$245.28	$245.30	$245.30
Purchase #5	$205.41	4.292%	$214.2262	$214.23	$214.25	$214.20
Purchase #6	$164.67	7.240%	$176.5921	$176.59	$176.60	$176.60
Purchase #7	$71.49	10.358%	$78.8949	$78.89	$78.90	$78.90
7 purchase totals =	$1,070.80		$1,150.2049	$1,150.21	$1,150.25	$1,150.20