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	$109.85	4.589%	$114.891	$114.89	$114.90	$114.90
Purchase #2	$97.89	5.757%	$103.5255	$103.53	$103.55	$103.50
Purchase #3	$103.66	7.225%	$111.1494	$111.15	$111.15	$111.10
Purchase #4	$12.58	4.790%	$13.1826	$13.18	$13.20	$13.20
Purchase #5	$13.73	4.705%	$14.376	$14.38	$14.40	$14.40
Purchase #6	$68.62	4.644%	$71.8067	$71.81	$71.80	$71.80
Purchase #7	$64.58	8.111%	$69.8181	$69.82	$69.80	$69.80
7 purchase totals =	$470.91		$498.7493	$498.76	$498.80	$498.70