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	$203.59	5.604%	$214.9992	$215.00	$215.00	$215.00
Purchase #2	$53.63	11.361%	$59.7229	$59.72	$59.70	$59.70
Purchase #3	$83.93	6.197%	$89.1311	$89.13	$89.15	$89.10
Purchase #4	$140.33	10.566%	$155.1573	$155.16	$155.15	$155.20
Purchase #5	$83.71	13.371%	$94.9029	$94.90	$94.90	$94.90
Purchase #6	$64.54	4.699%	$67.5727	$67.57	$67.55	$67.60
Purchase #7	$95.51	6.747%	$101.9541	$101.95	$101.95	$102.00
7 purchase totals =	$725.24		$783.4402	$783.43	$783.40	$783.50