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	$192.83	3.866%	$200.2848	$200.28	$200.30	$200.30
Purchase #2	$46.92	4.686%	$49.1187	$49.12	$49.10	$49.10
Purchase #3	$18.38	11.703%	$20.531	$20.53	$20.55	$20.50
Purchase #4	$123.78	5.835%	$131.0026	$131.00	$131.00	$131.00
Purchase #5	$208.96	11.637%	$233.2767	$233.28	$233.30	$233.30
Purchase #6	$145.92	13.808%	$166.0686	$166.07	$166.05	$166.10
Purchase #7	$11.85	3.459%	$12.2599	$12.26	$12.25	$12.30
7 purchase totals =	$748.64		$812.5423	$812.54	$812.55	$812.60