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	$210.32	7.112%	$225.278	$225.28	$225.30	$225.30
Purchase #2	$128.50	4.160%	$133.8456	$133.85	$133.85	$133.80
Purchase #3	$97.72	8.389%	$105.9177	$105.92	$105.90	$105.90
Purchase #4	$195.74	10.105%	$215.5195	$215.52	$215.50	$215.50
Purchase #5	$201.35	11.418%	$224.3401	$224.34	$224.35	$224.30
Purchase #6	$66.65	7.399%	$71.5814	$71.58	$71.60	$71.60
Purchase #7	$123.48	10.477%	$136.417	$136.42	$136.40	$136.40
7 purchase totals =	$1,023.76		$1,112.8993	$1,112.91	$1,112.90	$1,112.80