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	$98.70	8.729%	$107.3155	$107.32	$107.30	$107.30
Purchase #2	$208.50	4.306%	$217.478	$217.48	$217.50	$217.50
Purchase #3	$181.76	11.693%	$203.0132	$203.01	$203.00	$203.00
Purchase #4	$48.51	12.380%	$54.5155	$54.52	$54.50	$54.50
Purchase #5	$120.54	6.471%	$128.3401	$128.34	$128.35	$128.30
Purchase #6	$136.54	3.204%	$140.9147	$140.91	$140.90	$140.90
Purchase #7	$81.83	11.102%	$90.9148	$90.91	$90.90	$90.90
7 purchase totals =	$876.38		$942.4918	$942.49	$942.45	$942.40