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	$112.45	9.703%	$123.361	$123.36	$123.35	$123.40
Purchase #2	$171.72	9.227%	$187.5646	$187.56	$187.55	$187.60
Purchase #3	$238.27	7.315%	$255.6995	$255.70	$255.70	$255.70
Purchase #4	$150.46	7.573%	$161.8543	$161.85	$161.85	$161.90
Purchase #5	$81.48	11.810%	$91.1028	$91.10	$91.10	$91.10
Purchase #6	$238.67	6.292%	$253.6871	$253.69	$253.70	$253.70
Purchase #7	$236.97	7.755%	$255.347	$255.35	$255.35	$255.30
7 purchase totals =	$1,230.02		$1,328.6163	$1,328.61	$1,328.60	$1,328.70