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	$187.97	6.237%	$199.6937	$199.69	$199.70	$199.70
Purchase #2	$182.72	5.315%	$192.4316	$192.43	$192.45	$192.40
Purchase #3	$152.49	8.771%	$165.8649	$165.86	$165.85	$165.90
Purchase #4	$181.71	10.440%	$200.6805	$200.68	$200.70	$200.70
Purchase #5	$99.89	12.238%	$112.1145	$112.11	$112.10	$112.10
Purchase #6	$40.82	6.407%	$43.4353	$43.44	$43.45	$43.40
Purchase #7	$129.25	9.661%	$141.7368	$141.74	$141.75	$141.70
7 purchase totals =	$974.85		$1,055.9573	$1,055.95	$1,056.00	$1,055.90