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	$118.71	8.433%	$128.7208	$128.72	$128.70	$128.70
Purchase #2	$13.39	5.136%	$14.0777	$14.08	$14.10	$14.10
Purchase #3	$110.76	11.672%	$123.6879	$123.69	$123.70	$123.70
Purchase #4	$61.38	11.232%	$68.2742	$68.27	$68.25	$68.30
Purchase #5	$179.55	10.763%	$198.875	$198.88	$198.90	$198.90
Purchase #6	$35.87	13.156%	$40.5891	$40.59	$40.60	$40.60
Purchase #7	$91.34	11.597%	$101.9327	$101.93	$101.95	$101.90
7 purchase totals =	$611.00		$676.1574	$676.16	$676.20	$676.20