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	$68.29	6.282%	$72.58	$72.58	$72.60	$72.60
Purchase #2	$85.55	5.787%	$90.5008	$90.50	$90.50	$90.50
Purchase #3	$208.96	6.576%	$222.7012	$222.70	$222.70	$222.70
Purchase #4	$109.78	4.839%	$115.0923	$115.09	$115.10	$115.10
Purchase #5	$141.34	4.408%	$147.5703	$147.57	$147.55	$147.60
Purchase #6	$182.90	3.770%	$189.7953	$189.80	$189.80	$189.80
Purchase #7	$92.75	9.389%	$101.4583	$101.46	$101.45	$101.50
7 purchase totals =	$889.57		$939.6982	$939.70	$939.70	$939.80