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	$130.33	12.240%	$146.2824	$146.28	$146.30	$146.30
Purchase #2	$33.34	6.373%	$35.4648	$35.46	$35.45	$35.50
Purchase #3	$203.67	10.812%	$225.6908	$225.69	$225.70	$225.70
Purchase #4	$242.70	9.365%	$265.4289	$265.43	$265.45	$265.40
Purchase #5	$200.50	4.699%	$209.9215	$209.92	$209.90	$209.90
Purchase #6	$102.56	10.715%	$113.5493	$113.55	$113.55	$113.50
Purchase #7	$129.62	5.767%	$137.0952	$137.10	$137.10	$137.10
7 purchase totals =	$1,042.72		$1,133.4329	$1,133.43	$1,133.45	$1,133.40