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	$130.92	12.610%	$147.429	$147.43	$147.45	$147.40
Purchase #2	$76.70	10.258%	$84.5679	$84.57	$84.55	$84.60
Purchase #3	$55.54	3.200%	$57.3173	$57.32	$57.30	$57.30
Purchase #4	$133.82	8.381%	$145.0355	$145.04	$145.05	$145.00
Purchase #5	$153.79	10.222%	$169.5104	$169.51	$169.50	$169.50
Purchase #6	$110.46	11.453%	$123.111	$123.11	$123.10	$123.10
Purchase #7	$71.69	9.694%	$78.6396	$78.64	$78.65	$78.60
7 purchase totals =	$732.92		$805.6107	$805.62	$805.60	$805.50