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	$65.95	11.831%	$73.7525	$73.75	$73.75	$73.80
Purchase #2	$60.27	12.720%	$67.9363	$67.94	$67.95	$67.90
Purchase #3	$33.65	12.437%	$37.8351	$37.84	$37.85	$37.80
Purchase #4	$118.79	9.376%	$129.9278	$129.93	$129.95	$129.90
Purchase #5	$81.83	9.200%	$89.3584	$89.36	$89.35	$89.40
Purchase #6	$55.42	9.803%	$60.8528	$60.85	$60.85	$60.90
Purchase #7	$140.41	11.673%	$156.8001	$156.80	$156.80	$156.80
7 purchase totals =	$556.32		$616.4630	$616.47	$616.50	$616.50