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	$180.77	3.208%	$186.5691	$186.57	$186.55	$186.60
Purchase #2	$104.47	4.232%	$108.8912	$108.89	$108.90	$108.90
Purchase #3	$143.91	5.682%	$152.087	$152.09	$152.10	$152.10
Purchase #4	$43.61	13.841%	$49.6461	$49.65	$49.65	$49.60
Purchase #5	$88.51	12.188%	$99.2976	$99.30	$99.30	$99.30
Purchase #6	$7.35	7.275%	$7.8847	$7.88	$7.90	$7.90
Purchase #7	$115.87	10.350%	$127.8625	$127.86	$127.85	$127.90
7 purchase totals =	$684.49		$732.2382	$732.24	$732.25	$732.30