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	$97.56	11.782%	$109.0545	$109.05	$109.05	$109.10
Purchase #2	$216.83	7.670%	$233.4609	$233.46	$233.45	$233.50
Purchase #3	$12.42	8.665%	$13.4962	$13.50	$13.50	$13.50
Purchase #4	$220.41	12.775%	$248.5674	$248.57	$248.55	$248.60
Purchase #5	$139.25	11.331%	$155.0284	$155.03	$155.05	$155.00
Purchase #6	$149.91	10.795%	$166.0928	$166.09	$166.10	$166.10
Purchase #7	$225.29	6.627%	$240.22	$240.22	$240.20	$240.20
7 purchase totals =	$1,061.67		$1,165.9202	$1,165.92	$1,165.90	$1,166.00