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	$222.32	7.852%	$239.7766	$239.78	$239.80	$239.80
Purchase #2	$194.62	11.305%	$216.6218	$216.62	$216.60	$216.60
Purchase #3	$151.59	13.408%	$171.9152	$171.92	$171.90	$171.90
Purchase #4	$109.32	11.732%	$122.1454	$122.15	$122.15	$122.10
Purchase #5	$148.63	3.679%	$154.0981	$154.10	$154.10	$154.10
Purchase #6	$89.45	10.725%	$99.0435	$99.04	$99.05	$99.00
Purchase #7	$59.96	3.391%	$61.9932	$61.99	$62.00	$62.00
7 purchase totals =	$975.89		$1,065.5938	$1,065.60	$1,065.60	$1,065.50