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	$191.93	4.681%	$200.9142	$200.91	$200.90	$200.90
Purchase #2	$42.42	4.743%	$44.432	$44.43	$44.45	$44.40
Purchase #3	$206.91	7.562%	$222.5565	$222.56	$222.55	$222.60
Purchase #4	$98.97	3.545%	$102.4785	$102.48	$102.50	$102.50
Purchase #5	$198.78	13.599%	$225.8121	$225.81	$225.80	$225.80
Purchase #6	$108.35	7.820%	$116.823	$116.82	$116.80	$116.80
Purchase #7	$18.69	3.767%	$19.3941	$19.39	$19.40	$19.40
7 purchase totals =	$866.05		$932.4104	$932.40	$932.40	$932.40