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	$151.80	11.160%	$168.7409	$168.74	$168.75	$168.70
Purchase #2	$163.34	9.596%	$179.0141	$179.01	$179.00	$179.00
Purchase #3	$78.56	13.804%	$89.4044	$89.40	$89.40	$89.40
Purchase #4	$138.40	8.458%	$150.1059	$150.11	$150.10	$150.10
Purchase #5	$214.98	9.573%	$235.56	$235.56	$235.55	$235.60
Purchase #6	$37.83	5.341%	$39.8505	$39.85	$39.85	$39.90
Purchase #7	$212.83	13.643%	$241.8664	$241.87	$241.85	$241.90
7 purchase totals =	$997.74		$1,104.5422	$1,104.54	$1,104.50	$1,104.60