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	$173.53	13.203%	$196.4412	$196.44	$196.45	$196.40
Purchase #2	$155.93	10.196%	$171.8286	$171.83	$171.85	$171.80
Purchase #3	$121.53	6.320%	$129.2107	$129.21	$129.20	$129.20
Purchase #4	$48.35	12.706%	$54.4934	$54.49	$54.50	$54.50
Purchase #5	$219.89	10.319%	$242.5804	$242.58	$242.60	$242.60
Purchase #6	$40.92	6.622%	$43.6297	$43.63	$43.65	$43.60
Purchase #7	$99.40	5.470%	$104.8372	$104.84	$104.85	$104.80
7 purchase totals =	$859.55		$943.0212	$943.02	$943.10	$942.90