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	$197.38	9.393%	$215.9199	$215.92	$215.90	$215.90
Purchase #2	$101.88	7.839%	$109.8664	$109.87	$109.85	$109.90
Purchase #3	$117.69	8.589%	$127.7984	$127.80	$127.80	$127.80
Purchase #4	$106.93	5.559%	$112.8742	$112.87	$112.85	$112.90
Purchase #5	$159.89	3.234%	$165.0608	$165.06	$165.05	$165.10
Purchase #6	$165.47	13.630%	$188.0236	$188.02	$188.00	$188.00
Purchase #7	$226.88	12.856%	$256.0477	$256.05	$256.05	$256.00
7 purchase totals =	$1,076.12		$1,175.5910	$1,175.59	$1,175.50	$1,175.60