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	$33.97	13.855%	$38.6765	$38.68	$38.70	$38.70
Purchase #2	$238.51	11.477%	$265.8838	$265.88	$265.90	$265.90
Purchase #3	$17.26	7.623%	$18.5757	$18.58	$18.60	$18.60
Purchase #4	$109.53	13.459%	$124.2716	$124.27	$124.25	$124.30
Purchase #5	$157.60	3.111%	$162.5029	$162.50	$162.50	$162.50
Purchase #6	$184.73	8.437%	$200.3157	$200.32	$200.30	$200.30
Purchase #7	$217.54	10.424%	$240.2164	$240.22	$240.20	$240.20
7 purchase totals =	$959.14		$1,050.4426	$1,050.45	$1,050.45	$1,050.50