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	$31.93	7.637%	$34.3685	$34.37	$34.35	$34.40
Purchase #2	$35.76	13.111%	$40.4485	$40.45	$40.45	$40.40
Purchase #3	$51.31	3.525%	$53.1187	$53.12	$53.10	$53.10
Purchase #4	$17.74	5.620%	$18.737	$18.74	$18.75	$18.70
Purchase #5	$211.47	12.248%	$237.3708	$237.37	$237.35	$237.40
Purchase #6	$91.99	4.727%	$96.3384	$96.34	$96.35	$96.30
Purchase #7	$105.81	5.285%	$111.4021	$111.40	$111.40	$111.40
7 purchase totals =	$546.01		$591.7840	$591.79	$591.75	$591.70