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	$94.25	5.631%	$99.5572	$99.56	$99.55	$99.60
Purchase #2	$13.94	13.874%	$15.874	$15.87	$15.85	$15.90
Purchase #3	$233.94	8.341%	$253.4529	$253.45	$253.45	$253.50
Purchase #4	$128.31	10.691%	$142.0276	$142.03	$142.05	$142.00
Purchase #5	$59.93	10.627%	$66.2988	$66.30	$66.30	$66.30
Purchase #6	$35.92	9.513%	$39.3371	$39.34	$39.35	$39.30
Purchase #7	$67.41	12.538%	$75.8619	$75.86	$75.85	$75.90
7 purchase totals =	$633.70		$692.4095	$692.41	$692.40	$692.50