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	$117.59	7.561%	$126.481	$126.48	$126.50	$126.50
Purchase #2	$168.95	9.744%	$185.4125	$185.41	$185.40	$185.40
Purchase #3	$170.82	4.360%	$178.2678	$178.27	$178.25	$178.30
Purchase #4	$231.75	8.783%	$252.1046	$252.10	$252.10	$252.10
Purchase #5	$17.45	5.513%	$18.412	$18.41	$18.40	$18.40
Purchase #6	$163.78	7.647%	$176.3043	$176.30	$176.30	$176.30
Purchase #7	$73.42	12.290%	$82.4433	$82.44	$82.45	$82.40
7 purchase totals =	$943.76		$1,019.4255	$1,019.41	$1,019.40	$1,019.40