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	$103.37	7.402%	$111.0214	$111.02	$111.00	$111.00
Purchase #2	$43.94	7.103%	$47.0611	$47.06	$47.05	$47.10
Purchase #3	$40.81	9.129%	$44.5355	$44.54	$44.55	$44.50
Purchase #4	$113.88	11.625%	$127.1186	$127.12	$127.10	$127.10
Purchase #5	$84.48	6.445%	$89.9247	$89.92	$89.90	$89.90
Purchase #6	$124.48	12.116%	$139.562	$139.56	$139.55	$139.60
Purchase #7	$15.76	13.452%	$17.88	$17.88	$17.90	$17.90
7 purchase totals =	$526.72		$577.1033	$577.10	$577.05	$577.10