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	$104.28	9.866%	$114.5683	$114.57	$114.55	$114.60
Purchase #2	$151.88	11.373%	$169.1533	$169.15	$169.15	$169.20
Purchase #3	$234.78	4.507%	$245.3615	$245.36	$245.35	$245.40
Purchase #4	$54.88	4.226%	$57.1992	$57.20	$57.20	$57.20
Purchase #5	$121.81	8.221%	$131.824	$131.82	$131.80	$131.80
Purchase #6	$38.35	12.463%	$43.1296	$43.13	$43.15	$43.10
Purchase #7	$54.54	9.320%	$59.6231	$59.62	$59.60	$59.60
7 purchase totals =	$760.52		$820.8590	$820.85	$820.80	$820.90