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	$101.41	9.596%	$111.1413	$111.14	$111.15	$111.10
Purchase #2	$121.71	7.463%	$130.7932	$130.79	$130.80	$130.80
Purchase #3	$191.44	4.646%	$200.3343	$200.33	$200.35	$200.30
Purchase #4	$89.48	9.618%	$98.0862	$98.09	$98.10	$98.10
Purchase #5	$32.66	9.800%	$35.8607	$35.86	$35.85	$35.90
Purchase #6	$246.93	12.777%	$278.4802	$278.48	$278.50	$278.50
Purchase #7	$153.74	3.809%	$159.596	$159.60	$159.60	$159.60
7 purchase totals =	$937.37		$1,014.2919	$1,014.29	$1,014.35	$1,014.30