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	$133.71	13.400%	$151.6271	$151.63	$151.65	$151.60
Purchase #2	$102.27	10.151%	$112.6514	$112.65	$112.65	$112.70
Purchase #3	$149.30	8.271%	$161.6486	$161.65	$161.65	$161.60
Purchase #4	$43.36	4.488%	$45.306	$45.31	$45.30	$45.30
Purchase #5	$179.54	3.222%	$185.3248	$185.32	$185.30	$185.30
Purchase #6	$87.83	10.529%	$97.0776	$97.08	$97.10	$97.10
Purchase #7	$232.86	9.462%	$254.8932	$254.89	$254.90	$254.90
7 purchase totals =	$928.87		$1,008.5287	$1,008.53	$1,008.55	$1,008.50