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	$94.69	4.233%	$98.6982	$98.70	$98.70	$98.70
Purchase #2	$182.53	8.512%	$198.067	$198.07	$198.05	$198.10
Purchase #3	$65.46	10.822%	$72.5441	$72.54	$72.55	$72.50
Purchase #4	$59.48	12.786%	$67.0851	$67.09	$67.10	$67.10
Purchase #5	$55.99	7.801%	$60.3578	$60.36	$60.35	$60.40
Purchase #6	$239.88	5.691%	$253.5316	$253.53	$253.55	$253.50
Purchase #7	$191.89	12.489%	$215.8551	$215.86	$215.85	$215.90
7 purchase totals =	$889.92		$966.1389	$966.15	$966.15	$966.20