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	$134.68	12.413%	$151.3978	$151.40	$151.40	$151.40
Purchase #2	$155.93	13.504%	$176.9868	$176.99	$177.00	$177.00
Purchase #3	$117.39	11.650%	$131.0659	$131.07	$131.05	$131.10
Purchase #4	$209.30	5.556%	$220.9287	$220.93	$220.95	$220.90
Purchase #5	$89.50	11.620%	$99.8999	$99.90	$99.90	$99.90
Purchase #6	$190.93	4.199%	$198.9472	$198.95	$198.95	$198.90
Purchase #7	$172.74	13.825%	$196.6213	$196.62	$196.60	$196.60
7 purchase totals =	$1,070.47		$1,175.8476	$1,175.86	$1,175.85	$1,175.80