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	$212.85	9.599%	$233.2815	$233.28	$233.30	$233.30
Purchase #2	$41.56	8.419%	$45.0589	$45.06	$45.05	$45.10
Purchase #3	$31.69	10.725%	$35.0888	$35.09	$35.10	$35.10
Purchase #4	$89.51	7.569%	$96.285	$96.29	$96.30	$96.30
Purchase #5	$148.34	11.185%	$164.9318	$164.93	$164.95	$164.90
Purchase #6	$112.89	3.608%	$116.9631	$116.96	$116.95	$117.00
Purchase #7	$187.61	13.204%	$212.382	$212.38	$212.40	$212.40
7 purchase totals =	$824.45		$903.9911	$903.99	$904.05	$904.10