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	$221.57	10.810%	$245.5217	$245.52	$245.50	$245.50
Purchase #2	$10.30	6.151%	$10.9336	$10.93	$10.95	$10.90
Purchase #3	$61.77	3.209%	$63.7522	$63.75	$63.75	$63.80
Purchase #4	$131.64	5.855%	$139.3475	$139.35	$139.35	$139.30
Purchase #5	$104.43	5.223%	$109.8844	$109.88	$109.90	$109.90
Purchase #6	$171.65	12.517%	$193.1354	$193.14	$193.15	$193.10
Purchase #7	$56.64	10.281%	$62.4632	$62.46	$62.45	$62.50
7 purchase totals =	$758.00		$825.0380	$825.03	$825.05	$825.00