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	$167.85	5.253%	$176.6672	$176.67	$176.65	$176.70
Purchase #2	$56.49	13.258%	$63.9794	$63.98	$64.00	$64.00
Purchase #3	$51.92	13.545%	$58.9526	$58.95	$58.95	$59.00
Purchase #4	$22.50	8.363%	$24.3817	$24.38	$24.40	$24.40
Purchase #5	$55.47	7.304%	$59.5215	$59.52	$59.50	$59.50
Purchase #6	$189.59	5.612%	$200.2298	$200.23	$200.25	$200.20
Purchase #7	$71.54	7.272%	$76.7424	$76.74	$76.75	$76.70
7 purchase totals =	$615.36		$660.4746	$660.47	$660.50	$660.50