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	$128.41	10.168%	$141.4667	$141.47	$141.45	$141.50
Purchase #2	$187.95	10.346%	$207.3953	$207.40	$207.40	$207.40
Purchase #3	$38.67	12.840%	$43.6352	$43.64	$43.65	$43.60
Purchase #4	$69.79	11.557%	$77.8556	$77.86	$77.85	$77.90
Purchase #5	$176.91	7.689%	$190.5126	$190.51	$190.50	$190.50
Purchase #6	$23.41	4.524%	$24.4691	$24.47	$24.45	$24.50
Purchase #7	$18.36	10.531%	$20.2935	$20.29	$20.30	$20.30
7 purchase totals =	$643.50		$705.6280	$705.64	$705.60	$705.70