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	$158.90	4.508%	$166.0632	$166.06	$166.05	$166.10
Purchase #2	$122.81	3.744%	$127.408	$127.41	$127.40	$127.40
Purchase #3	$75.77	4.318%	$79.0417	$79.04	$79.05	$79.00
Purchase #4	$126.87	13.142%	$143.5433	$143.54	$143.55	$143.50
Purchase #5	$236.92	3.802%	$245.9277	$245.93	$245.95	$245.90
Purchase #6	$43.86	8.742%	$47.6942	$47.69	$47.70	$47.70
Purchase #7	$112.51	13.721%	$127.9475	$127.95	$127.95	$127.90
7 purchase totals =	$877.64		$937.6256	$937.62	$937.65	$937.50