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	$190.35	4.714%	$199.3231	$199.32	$199.30	$199.30
Purchase #2	$62.50	10.811%	$69.2569	$69.26	$69.25	$69.30
Purchase #3	$103.53	3.679%	$107.3389	$107.34	$107.35	$107.30
Purchase #4	$55.41	6.669%	$59.1053	$59.11	$59.10	$59.10
Purchase #5	$160.92	3.782%	$167.006	$167.01	$167.00	$167.00
Purchase #6	$32.61	11.859%	$36.4772	$36.48	$36.50	$36.50
Purchase #7	$27.35	6.379%	$29.0947	$29.09	$29.10	$29.10
7 purchase totals =	$632.67		$667.6021	$667.61	$667.60	$667.60