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	$164.80	4.815%	$172.7351	$172.74	$172.75	$172.70
Purchase #2	$182.50	7.511%	$196.2076	$196.21	$196.20	$196.20
Purchase #3	$19.76	3.833%	$20.5174	$20.52	$20.50	$20.50
Purchase #4	$57.43	13.774%	$65.3404	$65.34	$65.35	$65.30
Purchase #5	$100.44	5.637%	$106.1018	$106.10	$106.10	$106.10
Purchase #6	$112.32	8.821%	$122.2277	$122.23	$122.25	$122.20
Purchase #7	$120.25	9.215%	$131.331	$131.33	$131.35	$131.30
7 purchase totals =	$757.50		$814.4610	$814.47	$814.50	$814.30