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	$186.82	12.142%	$209.5037	$209.50	$209.50	$209.50
Purchase #2	$185.78	8.102%	$200.8319	$200.83	$200.85	$200.80
Purchase #3	$43.36	12.747%	$48.8871	$48.89	$48.90	$48.90
Purchase #4	$227.46	5.845%	$240.755	$240.76	$240.75	$240.80
Purchase #5	$86.51	10.689%	$95.7571	$95.76	$95.75	$95.80
Purchase #6	$49.96	10.804%	$55.3577	$55.36	$55.35	$55.40
Purchase #7	$181.35	5.818%	$191.9009	$191.90	$191.90	$191.90
7 purchase totals =	$961.24		$1,042.9934	$1,043.00	$1,043.00	$1,043.10