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	$144.54	6.738%	$154.2791	$154.28	$154.30	$154.30
Purchase #2	$89.26	6.392%	$94.9655	$94.97	$94.95	$95.00
Purchase #3	$146.43	5.292%	$154.1791	$154.18	$154.20	$154.20
Purchase #4	$79.78	12.250%	$89.5531	$89.55	$89.55	$89.60
Purchase #5	$18.95	12.234%	$21.2683	$21.27	$21.25	$21.30
Purchase #6	$33.87	4.701%	$35.4622	$35.46	$35.45	$35.50
Purchase #7	$231.31	6.560%	$246.4839	$246.48	$246.50	$246.50
7 purchase totals =	$744.14		$796.1912	$796.19	$796.20	$796.40