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	$116.94	9.357%	$127.8821	$127.88	$127.90	$127.90
Purchase #2	$182.56	6.440%	$194.3169	$194.32	$194.30	$194.30
Purchase #3	$241.94	9.129%	$264.0267	$264.03	$264.05	$264.00
Purchase #4	$96.32	3.722%	$99.905	$99.91	$99.90	$99.90
Purchase #5	$209.60	12.834%	$236.5001	$236.50	$236.50	$236.50
Purchase #6	$217.48	10.108%	$239.4629	$239.46	$239.45	$239.50
Purchase #7	$216.49	10.522%	$239.2691	$239.27	$239.25	$239.30
7 purchase totals =	$1,281.33		$1,401.3628	$1,401.37	$1,401.35	$1,401.40