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	$98.94	5.645%	$104.5252	$104.53	$104.55	$104.50
Purchase #2	$77.67	12.773%	$87.5908	$87.59	$87.60	$87.60
Purchase #3	$97.90	13.237%	$110.859	$110.86	$110.85	$110.90
Purchase #4	$209.44	12.443%	$235.5006	$235.50	$235.50	$235.50
Purchase #5	$158.31	8.730%	$172.1305	$172.13	$172.15	$172.10
Purchase #6	$171.33	11.311%	$190.7091	$190.71	$190.70	$190.70
Purchase #7	$150.41	11.578%	$167.8245	$167.82	$167.80	$167.80
7 purchase totals =	$964.00		$1,069.1397	$1,069.14	$1,069.15	$1,069.10