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	$68.80	5.683%	$72.7099	$72.71	$72.70	$72.70
Purchase #2	$15.54	4.202%	$16.193	$16.19	$16.20	$16.20
Purchase #3	$95.46	4.217%	$99.4855	$99.49	$99.50	$99.50
Purchase #4	$52.64	12.483%	$59.2111	$59.21	$59.20	$59.20
Purchase #5	$54.32	3.392%	$56.1625	$56.16	$56.15	$56.20
Purchase #6	$13.79	3.551%	$14.2797	$14.28	$14.30	$14.30
Purchase #7	$27.58	13.229%	$31.2286	$31.23	$31.25	$31.20
7 purchase totals =	$328.13		$349.2703	$349.27	$349.30	$349.30