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	$240.43	9.324%	$262.8477	$262.85	$262.85	$262.80
Purchase #2	$113.76	7.486%	$122.2761	$122.28	$122.30	$122.30
Purchase #3	$130.53	11.555%	$145.6127	$145.61	$145.60	$145.60
Purchase #4	$125.41	11.261%	$139.5324	$139.53	$139.55	$139.50
Purchase #5	$227.92	5.639%	$240.7724	$240.77	$240.75	$240.80
Purchase #6	$102.96	8.269%	$111.4738	$111.47	$111.45	$111.50
Purchase #7	$30.64	7.765%	$33.0192	$33.02	$33.00	$33.00
7 purchase totals =	$971.65		$1,055.5343	$1,055.53	$1,055.50	$1,055.50