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	$67.34	9.800%	$73.9393	$73.94	$73.95	$73.90
Purchase #2	$14.78	4.558%	$15.4537	$15.45	$15.45	$15.50
Purchase #3	$42.34	4.829%	$44.3846	$44.38	$44.40	$44.40
Purchase #4	$11.54	11.244%	$12.8376	$12.84	$12.85	$12.80
Purchase #5	$190.55	13.841%	$216.924	$216.92	$216.90	$216.90
Purchase #6	$209.93	7.119%	$224.8749	$224.87	$224.85	$224.90
Purchase #7	$79.53	5.445%	$83.8604	$83.86	$83.85	$83.90
7 purchase totals =	$616.01		$672.2745	$672.26	$672.25	$672.30