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	$63.30	7.146%	$67.8234	$67.82	$67.80	$67.80
Purchase #2	$164.93	12.492%	$185.5331	$185.53	$185.55	$185.50
Purchase #3	$80.90	12.272%	$90.828	$90.83	$90.85	$90.80
Purchase #4	$56.28	4.282%	$58.6899	$58.69	$58.70	$58.70
Purchase #5	$61.98	11.162%	$68.8982	$68.90	$68.90	$68.90
Purchase #6	$169.89	13.824%	$193.3756	$193.38	$193.40	$193.40
Purchase #7	$248.79	12.293%	$279.3738	$279.37	$279.35	$279.40
7 purchase totals =	$846.07		$944.5220	$944.52	$944.55	$944.50