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	$77.94	13.419%	$88.3988	$88.40	$88.40	$88.40
Purchase #2	$84.65	13.292%	$95.9017	$95.90	$95.90	$95.90
Purchase #3	$83.78	7.153%	$89.7728	$89.77	$89.75	$89.80
Purchase #4	$162.83	12.340%	$182.9232	$182.92	$182.90	$182.90
Purchase #5	$188.86	6.610%	$201.3436	$201.34	$201.35	$201.30
Purchase #6	$165.71	3.317%	$171.2066	$171.21	$171.20	$171.20
Purchase #7	$33.29	12.313%	$37.389	$37.39	$37.40	$37.40
7 purchase totals =	$797.06		$866.9357	$866.93	$866.90	$866.90