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	$130.47	9.214%	$142.4915	$142.49	$142.50	$142.50
Purchase #2	$23.87	11.418%	$26.5955	$26.60	$26.60	$26.60
Purchase #3	$119.66	7.283%	$128.3748	$128.37	$128.35	$128.40
Purchase #4	$52.69	12.406%	$59.2267	$59.23	$59.25	$59.20
Purchase #5	$133.46	10.756%	$147.815	$147.82	$147.80	$147.80
Purchase #6	$100.42	9.160%	$109.6185	$109.62	$109.60	$109.60
Purchase #7	$198.31	11.688%	$221.4885	$221.49	$221.50	$221.50
7 purchase totals =	$758.88		$835.6105	$835.62	$835.60	$835.60