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	$70.67	4.690%	$73.9844	$73.98	$74.00	$74.00
Purchase #2	$72.51	8.232%	$78.479	$78.48	$78.50	$78.50
Purchase #3	$250.95	4.625%	$262.5564	$262.56	$262.55	$262.60
Purchase #4	$94.85	10.109%	$104.4384	$104.44	$104.45	$104.40
Purchase #5	$169.68	10.192%	$186.9738	$186.97	$186.95	$187.00
Purchase #6	$158.78	9.516%	$173.8895	$173.89	$173.90	$173.90
Purchase #7	$95.41	5.326%	$100.4915	$100.49	$100.50	$100.50
7 purchase totals =	$912.85		$980.8130	$980.81	$980.85	$980.90