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	$147.53	7.705%	$158.8972	$158.90	$158.90	$158.90
Purchase #2	$56.98	4.416%	$59.4962	$59.50	$59.50	$59.50
Purchase #3	$38.95	10.241%	$42.9389	$42.94	$42.95	$42.90
Purchase #4	$221.77	8.608%	$240.86	$240.86	$240.85	$240.90
Purchase #5	$168.29	12.326%	$189.0334	$189.03	$189.05	$189.00
Purchase #6	$169.39	9.682%	$185.7903	$185.79	$185.80	$185.80
Purchase #7	$6.32	6.105%	$6.7058	$6.71	$6.70	$6.70
7 purchase totals =	$809.23		$883.7218	$883.73	$883.75	$883.70