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	$90.98	13.791%	$103.5271	$103.53	$103.55	$103.50
Purchase #2	$177.54	7.815%	$191.4148	$191.41	$191.40	$191.40
Purchase #3	$115.81	10.422%	$127.8797	$127.88	$127.90	$127.90
Purchase #4	$95.45	3.648%	$98.932	$98.93	$98.95	$98.90
Purchase #5	$232.65	3.807%	$241.507	$241.51	$241.50	$241.50
Purchase #6	$163.92	12.556%	$184.5018	$184.50	$184.50	$184.50
Purchase #7	$14.83	3.385%	$15.332	$15.33	$15.35	$15.30
7 purchase totals =	$891.18		$963.0944	$963.09	$963.15	$963.00