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	$39.59	13.763%	$45.0388	$45.04	$45.05	$45.00
Purchase #2	$73.29	7.724%	$78.9509	$78.95	$78.95	$79.00
Purchase #3	$22.34	3.452%	$23.1112	$23.11	$23.10	$23.10
Purchase #4	$120.76	11.551%	$134.709	$134.71	$134.70	$134.70
Purchase #5	$96.83	9.238%	$105.7752	$105.78	$105.80	$105.80
Purchase #6	$9.98	3.685%	$10.3478	$10.35	$10.35	$10.30
Purchase #7	$89.33	11.438%	$99.5476	$99.55	$99.55	$99.50
7 purchase totals =	$452.12		$497.4805	$497.49	$497.50	$497.40