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	$145.87	11.173%	$162.1681	$162.17	$162.15	$162.20
Purchase #2	$222.60	4.208%	$231.967	$231.97	$231.95	$232.00
Purchase #3	$83.46	7.384%	$89.6227	$89.62	$89.60	$89.60
Purchase #4	$35.40	13.728%	$40.2597	$40.26	$40.25	$40.30
Purchase #5	$122.53	10.725%	$135.6713	$135.67	$135.65	$135.70
Purchase #6	$240.25	4.699%	$251.5393	$251.54	$251.55	$251.50
Purchase #7	$133.45	13.355%	$151.2722	$151.27	$151.25	$151.30
7 purchase totals =	$983.56		$1,062.5003	$1,062.50	$1,062.40	$1,062.60