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	$249.29	13.821%	$283.7444	$283.74	$283.75	$283.70
Purchase #2	$18.49	11.355%	$20.5895	$20.59	$20.60	$20.60
Purchase #3	$66.43	11.282%	$73.9246	$73.92	$73.90	$73.90
Purchase #4	$94.59	6.564%	$100.7989	$100.80	$100.80	$100.80
Purchase #5	$74.79	5.483%	$78.8907	$78.89	$78.90	$78.90
Purchase #6	$213.63	8.660%	$232.1304	$232.13	$232.15	$232.10
Purchase #7	$245.32	11.512%	$273.5612	$273.56	$273.55	$273.60
7 purchase totals =	$962.54		$1,063.6397	$1,063.63	$1,063.65	$1,063.60