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	$134.29	5.664%	$141.8962	$141.90	$141.90	$141.90
Purchase #2	$203.46	10.684%	$225.1977	$225.20	$225.20	$225.20
Purchase #3	$101.67	11.765%	$113.6315	$113.63	$113.65	$113.60
Purchase #4	$189.25	12.196%	$212.3309	$212.33	$212.35	$212.30
Purchase #5	$126.54	3.634%	$131.1385	$131.14	$131.15	$131.10
Purchase #6	$128.34	12.523%	$144.412	$144.41	$144.40	$144.40
Purchase #7	$85.46	11.669%	$95.4323	$95.43	$95.45	$95.40
7 purchase totals =	$969.01		$1,064.0391	$1,064.04	$1,064.10	$1,063.90