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	$125.86	4.507%	$131.5325	$131.53	$131.55	$131.50
Purchase #2	$38.96	8.757%	$42.3717	$42.37	$42.35	$42.40
Purchase #3	$45.38	5.298%	$47.7842	$47.78	$47.80	$47.80
Purchase #4	$29.40	11.443%	$32.7642	$32.76	$32.75	$32.80
Purchase #5	$24.27	3.393%	$25.0935	$25.09	$25.10	$25.10
Purchase #6	$86.38	7.386%	$92.76	$92.76	$92.75	$92.80
Purchase #7	$222.30	11.119%	$247.0175	$247.02	$247.00	$247.00
7 purchase totals =	$572.55		$619.3236	$619.31	$619.30	$619.40