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	$183.82	8.742%	$199.8895	$199.89	$199.90	$199.90
Purchase #2	$48.99	13.185%	$55.4493	$55.45	$55.45	$55.40
Purchase #3	$82.38	11.285%	$91.6766	$91.68	$91.70	$91.70
Purchase #4	$165.45	6.822%	$176.737	$176.74	$176.75	$176.70
Purchase #5	$112.42	5.377%	$118.4648	$118.46	$118.45	$118.50
Purchase #6	$222.53	12.389%	$250.0992	$250.10	$250.10	$250.10
Purchase #7	$144.97	13.347%	$164.3191	$164.32	$164.30	$164.30
7 purchase totals =	$960.56		$1,056.6355	$1,056.64	$1,056.65	$1,056.60