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	$127.47	11.236%	$141.7925	$141.79	$141.80	$141.80
Purchase #2	$114.90	9.812%	$126.174	$126.17	$126.15	$126.20
Purchase #3	$67.69	9.739%	$74.2823	$74.28	$74.30	$74.30
Purchase #4	$25.45	11.145%	$28.2864	$28.29	$28.30	$28.30
Purchase #5	$18.83	6.631%	$20.0786	$20.08	$20.10	$20.10
Purchase #6	$178.83	6.761%	$190.9207	$190.92	$190.90	$190.90
Purchase #7	$160.67	3.616%	$166.4798	$166.48	$166.50	$166.50
7 purchase totals =	$693.84		$748.0143	$748.01	$748.05	$748.10