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	$130.68	9.368%	$142.9221	$142.92	$142.90	$142.90
Purchase #2	$238.47	7.128%	$255.4681	$255.47	$255.45	$255.50
Purchase #3	$89.64	4.867%	$94.0028	$94.00	$94.00	$94.00
Purchase #4	$104.66	9.874%	$114.9941	$114.99	$115.00	$115.00
Purchase #5	$149.41	12.256%	$167.7217	$167.72	$167.70	$167.70
Purchase #6	$43.99	4.419%	$45.9339	$45.93	$45.95	$45.90
Purchase #7	$154.35	11.340%	$171.8533	$171.85	$171.85	$171.90
7 purchase totals =	$911.20		$992.8960	$992.88	$992.85	$992.90