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	$162.60	5.167%	$171.0015	$171.00	$171.00	$171.00
Purchase #2	$10.51	7.554%	$11.3039	$11.30	$11.30	$11.30
Purchase #3	$130.68	12.773%	$147.3718	$147.37	$147.35	$147.40
Purchase #4	$78.49	8.110%	$84.8555	$84.86	$84.85	$84.90
Purchase #5	$61.38	8.518%	$66.6083	$66.61	$66.60	$66.60
Purchase #6	$86.39	4.229%	$90.0434	$90.04	$90.05	$90.00
Purchase #7	$52.52	13.621%	$59.6737	$59.67	$59.65	$59.70
7 purchase totals =	$582.57		$630.8581	$630.85	$630.80	$630.90