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	$197.70	12.665%	$222.7387	$222.74	$222.75	$222.70
Purchase #2	$171.43	11.845%	$191.7359	$191.74	$191.75	$191.70
Purchase #3	$105.46	11.207%	$117.2789	$117.28	$117.30	$117.30
Purchase #4	$137.69	11.638%	$153.7144	$153.71	$153.70	$153.70
Purchase #5	$68.79	11.744%	$76.8687	$76.87	$76.85	$76.90
Purchase #6	$86.48	4.684%	$90.5307	$90.53	$90.55	$90.50
Purchase #7	$248.92	8.592%	$270.3072	$270.31	$270.30	$270.30
7 purchase totals =	$1,016.47		$1,123.1745	$1,123.18	$1,123.20	$1,123.10