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	$64.36	11.713%	$71.8985	$71.90	$71.90	$71.90
Purchase #2	$75.50	9.251%	$82.4845	$82.48	$82.50	$82.50
Purchase #3	$180.37	13.106%	$204.0093	$204.01	$204.00	$204.00
Purchase #4	$97.53	3.433%	$100.8782	$100.88	$100.90	$100.90
Purchase #5	$23.88	7.390%	$25.6447	$25.64	$25.65	$25.60
Purchase #6	$109.76	11.534%	$122.4197	$122.42	$122.40	$122.40
Purchase #7	$75.55	8.836%	$82.2256	$82.23	$82.25	$82.20
7 purchase totals =	$626.95		$689.5605	$689.56	$689.60	$689.50