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	$167.29	13.480%	$189.8407	$189.84	$189.85	$189.80
Purchase #2	$39.61	8.279%	$42.8893	$42.89	$42.90	$42.90
Purchase #3	$95.48	5.258%	$100.5003	$100.50	$100.50	$100.50
Purchase #4	$190.43	12.248%	$213.7539	$213.75	$213.75	$213.80
Purchase #5	$57.58	12.545%	$64.8034	$64.80	$64.80	$64.80
Purchase #6	$142.57	3.139%	$147.0453	$147.05	$147.05	$147.00
Purchase #7	$47.30	13.671%	$53.7664	$53.77	$53.75	$53.80
7 purchase totals =	$740.26		$812.5993	$812.60	$812.60	$812.60