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	$100.73	10.543%	$111.35	$111.35	$111.35	$111.40
Purchase #2	$85.44	13.382%	$96.8736	$96.87	$96.85	$96.90
Purchase #3	$30.25	4.738%	$31.6832	$31.68	$31.70	$31.70
Purchase #4	$208.89	12.508%	$235.018	$235.02	$235.00	$235.00
Purchase #5	$242.84	13.166%	$274.8123	$274.81	$274.80	$274.80
Purchase #6	$118.56	3.311%	$122.4855	$122.49	$122.50	$122.50
Purchase #7	$92.32	13.538%	$104.8183	$104.82	$104.80	$104.80
7 purchase totals =	$879.03		$977.0409	$977.04	$977.00	$977.10