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	$32.34	8.595%	$35.1196	$35.12	$35.10	$35.10
Purchase #2	$228.57	11.771%	$255.475	$255.48	$255.50	$255.50
Purchase #3	$84.27	12.412%	$94.7296	$94.73	$94.75	$94.70
Purchase #4	$233.74	3.783%	$242.5824	$242.58	$242.60	$242.60
Purchase #5	$81.43	11.190%	$90.542	$90.54	$90.55	$90.50
Purchase #6	$244.46	6.805%	$261.0955	$261.10	$261.10	$261.10
Purchase #7	$211.90	10.229%	$233.5753	$233.58	$233.60	$233.60
7 purchase totals =	$1,116.71		$1,213.1194	$1,213.13	$1,213.20	$1,213.10