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	$246.37	5.499%	$259.9179	$259.92	$259.90	$259.90
Purchase #2	$145.51	4.107%	$151.4861	$151.49	$151.50	$151.50
Purchase #3	$139.29	3.524%	$144.1986	$144.20	$144.20	$144.20
Purchase #4	$46.31	3.411%	$47.8896	$47.89	$47.90	$47.90
Purchase #5	$31.48	13.257%	$35.6533	$35.65	$35.65	$35.70
Purchase #6	$92.74	8.489%	$100.6127	$100.61	$100.60	$100.60
Purchase #7	$239.98	12.111%	$269.044	$269.04	$269.05	$269.00
7 purchase totals =	$941.68		$1,008.8022	$1,008.80	$1,008.80	$1,008.80