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	$55.65	9.650%	$61.0202	$61.02	$61.00	$61.00
Purchase #2	$19.62	7.410%	$21.0738	$21.07	$21.05	$21.10
Purchase #3	$29.35	12.801%	$33.1071	$33.11	$33.10	$33.10
Purchase #4	$31.51	11.636%	$35.1765	$35.18	$35.20	$35.20
Purchase #5	$192.31	4.242%	$200.4678	$200.47	$200.45	$200.50
Purchase #6	$73.50	9.522%	$80.4987	$80.50	$80.50	$80.50
Purchase #7	$43.28	7.524%	$46.5364	$46.54	$46.55	$46.50
7 purchase totals =	$445.22		$477.8805	$477.89	$477.85	$477.90