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	$206.64	11.115%	$229.608	$229.61	$229.60	$229.60
Purchase #2	$166.65	8.340%	$180.5486	$180.55	$180.55	$180.50
Purchase #3	$241.34	9.821%	$265.042	$265.04	$265.05	$265.00
Purchase #4	$48.25	7.612%	$51.9228	$51.92	$51.90	$51.90
Purchase #5	$81.96	12.407%	$92.1288	$92.13	$92.15	$92.10
Purchase #6	$30.31	5.219%	$31.8919	$31.89	$31.90	$31.90
Purchase #7	$139.94	11.413%	$155.9114	$155.91	$155.90	$155.90
7 purchase totals =	$915.09		$1,007.0535	$1,007.05	$1,007.05	$1,006.90