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	$140.66	12.601%	$158.3846	$158.38	$158.40	$158.40
Purchase #2	$184.75	4.219%	$192.5446	$192.54	$192.55	$192.50
Purchase #3	$18.56	10.118%	$20.4379	$20.44	$20.45	$20.40
Purchase #4	$210.81	13.861%	$240.0304	$240.03	$240.05	$240.00
Purchase #5	$103.47	6.824%	$110.5308	$110.53	$110.55	$110.50
Purchase #6	$176.47	8.274%	$191.0711	$191.07	$191.05	$191.10
Purchase #7	$143.55	3.711%	$148.8771	$148.88	$148.90	$148.90
7 purchase totals =	$978.27		$1,061.8765	$1,061.87	$1,061.95	$1,061.80