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	$233.51	12.362%	$262.3765	$262.38	$262.40	$262.40
Purchase #2	$73.48	10.799%	$81.4151	$81.42	$81.40	$81.40
Purchase #3	$120.36	9.341%	$131.6028	$131.60	$131.60	$131.60
Purchase #4	$63.39	13.302%	$71.8221	$71.82	$71.80	$71.80
Purchase #5	$51.76	7.724%	$55.7579	$55.76	$55.75	$55.80
Purchase #6	$81.86	9.857%	$89.9289	$89.93	$89.95	$89.90
Purchase #7	$49.51	11.485%	$55.1962	$55.20	$55.20	$55.20
7 purchase totals =	$673.87		$748.0995	$748.11	$748.10	$748.10