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	$181.94	9.602%	$199.4099	$199.41	$199.40	$199.40
Purchase #2	$210.49	6.367%	$223.8919	$223.89	$223.90	$223.90
Purchase #3	$171.33	4.723%	$179.4219	$179.42	$179.40	$179.40
Purchase #4	$59.34	11.291%	$66.0401	$66.04	$66.05	$66.00
Purchase #5	$28.80	7.328%	$30.9105	$30.91	$30.90	$30.90
Purchase #6	$164.34	12.619%	$185.0781	$185.08	$185.10	$185.10
Purchase #7	$169.83	7.169%	$182.0051	$182.01	$182.00	$182.00
7 purchase totals =	$986.07		$1,066.7575	$1,066.76	$1,066.75	$1,066.70