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	$211.90	5.202%	$222.923	$222.92	$222.90	$222.90
Purchase #2	$57.33	8.643%	$62.285	$62.29	$62.30	$62.30
Purchase #3	$212.51	7.589%	$228.6374	$228.64	$228.65	$228.60
Purchase #4	$188.83	9.629%	$207.0124	$207.01	$207.00	$207.00
Purchase #5	$39.59	7.569%	$42.5866	$42.59	$42.60	$42.60
Purchase #6	$21.41	6.587%	$22.8203	$22.82	$22.80	$22.80
Purchase #7	$6.57	11.353%	$7.3159	$7.32	$7.30	$7.30
7 purchase totals =	$738.14		$793.5806	$793.59	$793.55	$793.50