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	$233.83	5.679%	$247.1092	$247.11	$247.10	$247.10
Purchase #2	$241.77	8.580%	$262.5139	$262.51	$262.50	$262.50
Purchase #3	$75.31	11.435%	$83.9217	$83.92	$83.90	$83.90
Purchase #4	$57.98	8.336%	$62.8132	$62.81	$62.80	$62.80
Purchase #5	$54.55	8.765%	$59.3313	$59.33	$59.35	$59.30
Purchase #6	$169.31	13.634%	$192.3937	$192.39	$192.40	$192.40
Purchase #7	$176.96	10.751%	$195.985	$195.99	$196.00	$196.00
7 purchase totals =	$1,009.71		$1,104.0680	$1,104.06	$1,104.05	$1,104.00