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	$151.27	4.371%	$157.882	$157.88	$157.90	$157.90
Purchase #2	$7.89	7.786%	$8.5043	$8.50	$8.50	$8.50
Purchase #3	$95.53	11.658%	$106.6669	$106.67	$106.65	$106.70
Purchase #4	$120.47	6.565%	$128.3789	$128.38	$128.40	$128.40
Purchase #5	$165.42	5.785%	$174.9895	$174.99	$175.00	$175.00
Purchase #6	$109.89	4.181%	$114.4845	$114.48	$114.50	$114.50
Purchase #7	$97.26	8.517%	$105.5436	$105.54	$105.55	$105.50
7 purchase totals =	$747.73		$796.4497	$796.44	$796.50	$796.50