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	$131.80	12.642%	$148.4622	$148.46	$148.45	$148.50
Purchase #2	$102.53	9.361%	$112.1278	$112.13	$112.15	$112.10
Purchase #3	$70.56	3.141%	$72.7763	$72.78	$72.80	$72.80
Purchase #4	$120.95	8.606%	$131.359	$131.36	$131.35	$131.40
Purchase #5	$239.85	13.368%	$271.9131	$271.91	$271.90	$271.90
Purchase #6	$130.55	11.652%	$145.7617	$145.76	$145.75	$145.80
Purchase #7	$39.41	10.671%	$43.6154	$43.62	$43.60	$43.60
7 purchase totals =	$835.65		$926.0155	$926.02	$926.00	$926.10