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	$243.89	4.828%	$255.665	$255.67	$255.65	$255.70
Purchase #2	$188.96	8.151%	$204.3621	$204.36	$204.35	$204.40
Purchase #3	$178.52	4.132%	$185.8964	$185.90	$185.90	$185.90
Purchase #4	$92.59	10.807%	$102.5962	$102.60	$102.60	$102.60
Purchase #5	$112.25	9.780%	$123.2281	$123.23	$123.25	$123.20
Purchase #6	$127.64	9.766%	$140.1053	$140.11	$140.10	$140.10
Purchase #7	$29.56	10.143%	$32.5583	$32.56	$32.55	$32.60
7 purchase totals =	$973.41		$1,044.4114	$1,044.43	$1,044.40	$1,044.50