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	$217.67	8.366%	$235.8803	$235.88	$235.90	$235.90
Purchase #2	$172.90	10.821%	$191.6095	$191.61	$191.60	$191.60
Purchase #3	$79.96	13.743%	$90.9489	$90.95	$90.95	$90.90
Purchase #4	$125.44	6.785%	$133.9511	$133.95	$133.95	$134.00
Purchase #5	$183.61	12.133%	$205.8874	$205.89	$205.90	$205.90
Purchase #6	$193.62	12.225%	$217.29	$217.29	$217.30	$217.30
Purchase #7	$60.94	7.564%	$65.5495	$65.55	$65.55	$65.50
7 purchase totals =	$1,034.14		$1,141.1167	$1,141.12	$1,141.15	$1,141.10