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	$104.53	11.700%	$116.76	$116.76	$116.75	$116.80
Purchase #2	$72.67	13.576%	$82.5357	$82.54	$82.55	$82.50
Purchase #3	$130.37	12.352%	$146.4733	$146.47	$146.45	$146.50
Purchase #4	$200.40	10.416%	$221.2737	$221.27	$221.25	$221.30
Purchase #5	$176.87	12.820%	$199.5447	$199.54	$199.55	$199.50
Purchase #6	$168.32	3.377%	$174.0042	$174.00	$174.00	$174.00
Purchase #7	$64.88	8.305%	$70.2683	$70.27	$70.25	$70.30
7 purchase totals =	$918.04		$1,010.8599	$1,010.85	$1,010.80	$1,010.90