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	$150.77	12.679%	$169.8861	$169.89	$169.90	$169.90
Purchase #2	$38.75	13.119%	$43.8336	$43.83	$43.85	$43.80
Purchase #3	$13.95	6.726%	$14.8883	$14.89	$14.90	$14.90
Purchase #4	$118.96	9.425%	$130.172	$130.17	$130.15	$130.20
Purchase #5	$55.91	5.211%	$58.8235	$58.82	$58.80	$58.80
Purchase #6	$190.67	12.712%	$214.908	$214.91	$214.90	$214.90
Purchase #7	$240.37	4.123%	$250.2805	$250.28	$250.30	$250.30
7 purchase totals =	$809.38		$882.7920	$882.79	$882.80	$882.80