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	$135.79	8.694%	$147.5956	$147.60	$147.60	$147.60
Purchase #2	$196.36	10.864%	$217.6926	$217.69	$217.70	$217.70
Purchase #3	$245.40	12.502%	$276.0799	$276.08	$276.10	$276.10
Purchase #4	$82.54	8.548%	$89.5955	$89.60	$89.60	$89.60
Purchase #5	$157.45	3.456%	$162.8915	$162.89	$162.90	$162.90
Purchase #6	$99.26	4.373%	$103.6006	$103.60	$103.60	$103.60
Purchase #7	$206.49	9.742%	$226.6063	$226.61	$226.60	$226.60
7 purchase totals =	$1,123.29		$1,224.0620	$1,224.07	$1,224.10	$1,224.10