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	$51.30	7.475%	$55.1347	$55.13	$55.15	$55.10
Purchase #2	$42.81	6.203%	$45.4655	$45.47	$45.45	$45.50
Purchase #3	$141.81	4.572%	$148.2936	$148.29	$148.30	$148.30
Purchase #4	$28.67	6.507%	$30.5356	$30.54	$30.55	$30.50
Purchase #5	$31.80	10.463%	$35.1272	$35.13	$35.15	$35.10
Purchase #6	$38.91	11.487%	$43.3796	$43.38	$43.40	$43.40
Purchase #7	$82.51	8.433%	$89.4681	$89.47	$89.45	$89.50
7 purchase totals =	$417.81		$447.4043	$447.41	$447.45	$447.40