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	$199.36	4.682%	$208.694	$208.69	$208.70	$208.70
Purchase #2	$133.80	9.786%	$146.8937	$146.89	$146.90	$146.90
Purchase #3	$169.89	11.170%	$188.8667	$188.87	$188.85	$188.90
Purchase #4	$171.63	5.218%	$180.5857	$180.59	$180.60	$180.60
Purchase #5	$121.93	3.760%	$126.5146	$126.51	$126.50	$126.50
Purchase #6	$89.52	10.569%	$98.9814	$98.98	$99.00	$99.00
Purchase #7	$219.34	9.849%	$240.9428	$240.94	$240.95	$240.90
7 purchase totals =	$1,105.47		$1,191.4789	$1,191.47	$1,191.50	$1,191.50