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	$54.87	9.551%	$60.1106	$60.11	$60.10	$60.10
Purchase #2	$35.63	11.863%	$39.8568	$39.86	$39.85	$39.90
Purchase #3	$53.54	10.603%	$59.2168	$59.22	$59.20	$59.20
Purchase #4	$238.50	11.147%	$265.0856	$265.09	$265.10	$265.10
Purchase #5	$114.27	9.867%	$125.545	$125.55	$125.55	$125.50
Purchase #6	$120.38	11.198%	$133.8602	$133.86	$133.85	$133.90
Purchase #7	$98.92	12.704%	$111.4868	$111.49	$111.50	$111.50
7 purchase totals =	$716.11		$795.1618	$795.18	$795.15	$795.20