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	$219.64	6.228%	$233.3192	$233.32	$233.30	$233.30
Purchase #2	$242.62	7.765%	$261.4594	$261.46	$261.45	$261.50
Purchase #3	$220.94	9.601%	$242.1524	$242.15	$242.15	$242.20
Purchase #4	$55.93	6.229%	$59.4139	$59.41	$59.40	$59.40
Purchase #5	$216.51	8.388%	$234.6709	$234.67	$234.65	$234.70
Purchase #6	$45.29	12.754%	$51.0663	$51.07	$51.05	$51.10
Purchase #7	$35.67	5.322%	$37.5684	$37.57	$37.55	$37.60
7 purchase totals =	$1,036.60		$1,119.6505	$1,119.65	$1,119.55	$1,119.80