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	$68.57	4.482%	$71.6433	$71.64	$71.65	$71.60
Purchase #2	$103.63	12.474%	$116.5568	$116.56	$116.55	$116.60
Purchase #3	$19.64	4.192%	$20.4633	$20.46	$20.45	$20.50
Purchase #4	$123.59	13.106%	$139.7877	$139.79	$139.80	$139.80
Purchase #5	$130.87	9.381%	$143.1469	$143.15	$143.15	$143.10
Purchase #6	$235.71	6.283%	$250.5197	$250.52	$250.50	$250.50
Purchase #7	$144.52	9.378%	$158.0731	$158.07	$158.05	$158.10
7 purchase totals =	$826.53		$900.1908	$900.19	$900.15	$900.20