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	$84.42	12.668%	$95.1143	$95.11	$95.10	$95.10
Purchase #2	$84.43	3.430%	$87.3259	$87.33	$87.35	$87.30
Purchase #3	$69.81	13.723%	$79.39	$79.39	$79.40	$79.40
Purchase #4	$134.50	12.614%	$151.4658	$151.47	$151.45	$151.50
Purchase #5	$161.88	12.840%	$182.6654	$182.67	$182.65	$182.70
Purchase #6	$54.47	9.642%	$59.722	$59.72	$59.70	$59.70
Purchase #7	$213.76	5.654%	$225.846	$225.85	$225.85	$225.80
7 purchase totals =	$803.27		$881.5294	$881.54	$881.50	$881.50