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	$47.29	12.145%	$53.0334	$53.03	$53.05	$53.00
Purchase #2	$34.81	3.259%	$35.9445	$35.94	$35.95	$35.90
Purchase #3	$167.90	10.405%	$185.37	$185.37	$185.35	$185.40
Purchase #4	$5.61	9.167%	$6.1243	$6.12	$6.10	$6.10
Purchase #5	$78.49	5.602%	$82.887	$82.89	$82.90	$82.90
Purchase #6	$109.97	8.342%	$119.1437	$119.14	$119.15	$119.10
Purchase #7	$19.90	4.368%	$20.7692	$20.77	$20.75	$20.80
7 purchase totals =	$463.97		$503.2721	$503.26	$503.25	$503.20