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	$54.96	8.577%	$59.6739	$59.67	$59.65	$59.70
Purchase #2	$106.34	11.267%	$118.3213	$118.32	$118.30	$118.30
Purchase #3	$18.59	7.466%	$19.9779	$19.98	$20.00	$20.00
Purchase #4	$81.83	6.272%	$86.9624	$86.96	$86.95	$87.00
Purchase #5	$23.53	4.137%	$24.5034	$24.50	$24.50	$24.50
Purchase #6	$28.94	10.487%	$31.9749	$31.97	$31.95	$32.00
Purchase #7	$42.46	7.684%	$45.7226	$45.72	$45.70	$45.70
7 purchase totals =	$356.65		$387.1364	$387.12	$387.05	$387.20