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	$82.75	8.220%	$89.5521	$89.55	$89.55	$89.60
Purchase #2	$38.47	12.476%	$43.2695	$43.27	$43.25	$43.30
Purchase #3	$79.36	13.668%	$90.2069	$90.21	$90.20	$90.20
Purchase #4	$205.49	10.872%	$227.8309	$227.83	$227.85	$227.80
Purchase #5	$237.51	12.474%	$267.137	$267.14	$267.15	$267.10
Purchase #6	$153.49	5.123%	$161.3533	$161.35	$161.35	$161.40
Purchase #7	$87.52	11.621%	$97.6907	$97.69	$97.70	$97.70
7 purchase totals =	$884.59		$977.0404	$977.04	$977.05	$977.10