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	$86.49	13.135%	$97.8505	$97.85	$97.85	$97.90
Purchase #2	$127.69	7.166%	$136.8403	$136.84	$136.85	$136.80
Purchase #3	$196.78	10.556%	$217.5521	$217.55	$217.55	$217.60
Purchase #4	$197.69	9.210%	$215.8972	$215.90	$215.90	$215.90
Purchase #5	$179.59	11.595%	$200.4135	$200.41	$200.40	$200.40
Purchase #6	$27.27	13.471%	$30.9435	$30.94	$30.95	$30.90
Purchase #7	$149.61	11.624%	$167.0007	$167.00	$167.00	$167.00
7 purchase totals =	$965.12		$1,066.4978	$1,066.49	$1,066.50	$1,066.50