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	$196.48	6.491%	$209.2335	$209.23	$209.25	$209.20
Purchase #2	$106.83	9.443%	$116.918	$116.92	$116.90	$116.90
Purchase #3	$189.87	4.834%	$199.0483	$199.05	$199.05	$199.00
Purchase #4	$50.87	4.284%	$53.0493	$53.05	$53.05	$53.00
Purchase #5	$87.57	9.307%	$95.7201	$95.72	$95.70	$95.70
Purchase #6	$198.32	12.632%	$223.3718	$223.37	$223.35	$223.40
Purchase #7	$101.70	10.431%	$112.3083	$112.31	$112.30	$112.30
7 purchase totals =	$931.64		$1,009.6493	$1,009.65	$1,009.60	$1,009.50