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	$221.57	7.576%	$238.3561	$238.36	$238.35	$238.40
Purchase #2	$90.29	3.441%	$93.3969	$93.40	$93.40	$93.40
Purchase #3	$18.64	11.770%	$20.8339	$20.83	$20.85	$20.80
Purchase #4	$85.34	4.736%	$89.3817	$89.38	$89.40	$89.40
Purchase #5	$23.65	4.231%	$24.6506	$24.65	$24.65	$24.70
Purchase #6	$192.26	12.334%	$215.9733	$215.97	$215.95	$216.00
Purchase #7	$162.72	5.352%	$171.4288	$171.43	$171.45	$171.40
7 purchase totals =	$794.47		$854.0213	$854.02	$854.05	$854.10