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	$182.82	9.668%	$200.495	$200.50	$200.50	$200.50
Purchase #2	$234.28	13.335%	$265.5212	$265.52	$265.50	$265.50
Purchase #3	$42.56	12.741%	$47.9826	$47.98	$48.00	$48.00
Purchase #4	$135.96	10.457%	$150.1773	$150.18	$150.20	$150.20
Purchase #5	$7.47	5.705%	$7.8962	$7.90	$7.90	$7.90
Purchase #6	$238.56	8.787%	$259.5223	$259.52	$259.50	$259.50
Purchase #7	$144.91	3.138%	$149.4573	$149.46	$149.45	$149.50
7 purchase totals =	$986.56		$1,081.0519	$1,081.06	$1,081.05	$1,081.10