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	$197.57	8.232%	$213.834	$213.83	$213.85	$213.80
Purchase #2	$212.97	5.138%	$223.9124	$223.91	$223.90	$223.90
Purchase #3	$39.39	11.143%	$43.7792	$43.78	$43.80	$43.80
Purchase #4	$81.38	8.828%	$88.5642	$88.56	$88.55	$88.60
Purchase #5	$39.56	7.701%	$42.6065	$42.61	$42.60	$42.60
Purchase #6	$194.67	3.156%	$200.8138	$200.81	$200.80	$200.80
Purchase #7	$98.26	10.269%	$108.3503	$108.35	$108.35	$108.40
7 purchase totals =	$863.80		$921.8604	$921.85	$921.85	$921.90