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	$160.47	4.846%	$168.2464	$168.25	$168.25	$168.20
Purchase #2	$229.61	8.822%	$249.8662	$249.87	$249.85	$249.90
Purchase #3	$112.81	6.509%	$120.1528	$120.15	$120.15	$120.20
Purchase #4	$86.53	8.546%	$93.9249	$93.92	$93.90	$93.90
Purchase #5	$179.77	6.595%	$191.6258	$191.63	$191.65	$191.60
Purchase #6	$88.98	7.296%	$95.472	$95.47	$95.45	$95.50
Purchase #7	$233.63	12.831%	$263.6071	$263.61	$263.60	$263.60
7 purchase totals =	$1,091.80		$1,182.8952	$1,182.90	$1,182.85	$1,182.90