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	$142.55	11.718%	$159.254	$159.25	$159.25	$159.30
Purchase #2	$137.88	5.276%	$145.1545	$145.15	$145.15	$145.20
Purchase #3	$45.59	12.525%	$51.3001	$51.30	$51.30	$51.30
Purchase #4	$62.84	6.523%	$66.9391	$66.94	$66.95	$66.90
Purchase #5	$89.67	10.798%	$99.3526	$99.35	$99.35	$99.40
Purchase #6	$125.77	8.491%	$136.4491	$136.45	$136.45	$136.40
Purchase #7	$173.35	12.198%	$194.4952	$194.50	$194.50	$194.50
7 purchase totals =	$777.65		$852.9446	$852.94	$852.95	$853.00