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	$219.46	10.285%	$242.0315	$242.03	$242.05	$242.00
Purchase #2	$120.33	6.580%	$128.2477	$128.25	$128.25	$128.20
Purchase #3	$233.29	9.502%	$255.4572	$255.46	$255.45	$255.50
Purchase #4	$181.89	7.828%	$196.1283	$196.13	$196.15	$196.10
Purchase #5	$61.65	5.575%	$65.087	$65.09	$65.10	$65.10
Purchase #6	$9.50	8.655%	$10.3222	$10.32	$10.30	$10.30
Purchase #7	$169.55	8.507%	$183.9736	$183.97	$183.95	$184.00
7 purchase totals =	$995.67		$1,081.2475	$1,081.25	$1,081.25	$1,081.20