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	$69.30	8.352%	$75.0879	$75.09	$75.10	$75.10
Purchase #2	$15.98	5.612%	$16.8768	$16.88	$16.90	$16.90
Purchase #3	$84.98	5.472%	$89.6301	$89.63	$89.65	$89.60
Purchase #4	$34.79	8.313%	$37.6821	$37.68	$37.70	$37.70
Purchase #5	$85.44	6.378%	$90.8894	$90.89	$90.90	$90.90
Purchase #6	$162.56	3.679%	$168.5406	$168.54	$168.55	$168.50
Purchase #7	$26.91	11.106%	$29.8986	$29.90	$29.90	$29.90
7 purchase totals =	$479.96		$508.6055	$508.61	$508.70	$508.60