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	$94.97	6.213%	$100.8705	$100.87	$100.85	$100.90
Purchase #2	$188.31	4.471%	$196.7293	$196.73	$196.75	$196.70
Purchase #3	$125.54	9.842%	$137.8956	$137.90	$137.90	$137.90
Purchase #4	$13.82	12.817%	$15.5913	$15.59	$15.60	$15.60
Purchase #5	$186.33	13.619%	$211.7063	$211.71	$211.70	$211.70
Purchase #6	$108.44	4.193%	$112.9869	$112.99	$113.00	$113.00
Purchase #7	$166.43	13.311%	$188.5835	$188.58	$188.60	$188.60
7 purchase totals =	$883.84		$964.3634	$964.37	$964.40	$964.40