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	$59.46	7.753%	$64.0699	$64.07	$64.05	$64.10
Purchase #2	$123.93	3.162%	$127.8487	$127.85	$127.85	$127.80
Purchase #3	$216.91	7.487%	$233.1501	$233.15	$233.15	$233.20
Purchase #4	$192.27	4.342%	$200.6184	$200.62	$200.60	$200.60
Purchase #5	$126.40	4.354%	$131.9035	$131.90	$131.90	$131.90
Purchase #6	$15.94	4.488%	$16.6554	$16.66	$16.65	$16.70
Purchase #7	$39.87	6.800%	$42.5812	$42.58	$42.60	$42.60
7 purchase totals =	$774.78		$816.8272	$816.83	$816.80	$816.90