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	$90.59	10.177%	$99.8093	$99.81	$99.80	$99.80
Purchase #2	$69.65	5.318%	$73.354	$73.35	$73.35	$73.40
Purchase #3	$180.97	9.754%	$198.6218	$198.62	$198.60	$198.60
Purchase #4	$149.83	3.189%	$154.6081	$154.61	$154.60	$154.60
Purchase #5	$148.28	11.807%	$165.7874	$165.79	$165.80	$165.80
Purchase #6	$250.80	11.748%	$280.264	$280.26	$280.25	$280.30
Purchase #7	$226.48	12.411%	$254.5884	$254.59	$254.60	$254.60
7 purchase totals =	$1,116.60		$1,227.0330	$1,227.03	$1,227.00	$1,227.10