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	$97.86	13.716%	$111.2825	$111.28	$111.30	$111.30
Purchase #2	$41.87	9.269%	$45.7509	$45.75	$45.75	$45.80
Purchase #3	$82.54	10.828%	$91.4774	$91.48	$91.50	$91.50
Purchase #4	$213.83	3.286%	$220.8565	$220.86	$220.85	$220.90
Purchase #5	$220.63	6.355%	$234.651	$234.65	$234.65	$234.70
Purchase #6	$155.61	11.515%	$173.5285	$173.53	$173.55	$173.50
Purchase #7	$181.83	9.296%	$198.7329	$198.73	$198.75	$198.70
7 purchase totals =	$994.17		$1,076.2797	$1,076.28	$1,076.35	$1,076.40