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	$142.90	6.407%	$152.0556	$152.06	$152.05	$152.10
Purchase #2	$211.40	12.314%	$237.4318	$237.43	$237.45	$237.40
Purchase #3	$81.42	4.570%	$85.1409	$85.14	$85.15	$85.10
Purchase #4	$157.93	6.612%	$168.3723	$168.37	$168.35	$168.40
Purchase #5	$100.95	5.790%	$106.795	$106.80	$106.80	$106.80
Purchase #6	$108.94	9.573%	$119.3688	$119.37	$119.35	$119.40
Purchase #7	$238.78	13.257%	$270.4351	$270.44	$270.45	$270.40
7 purchase totals =	$1,042.32		$1,139.5995	$1,139.61	$1,139.60	$1,139.60