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	$57.46	10.457%	$63.4686	$63.47	$63.45	$63.50
Purchase #2	$10.59	12.385%	$11.9016	$11.90	$11.90	$11.90
Purchase #3	$176.39	6.424%	$187.7213	$187.72	$187.70	$187.70
Purchase #4	$156.54	9.819%	$171.9107	$171.91	$171.90	$171.90
Purchase #5	$201.52	13.143%	$228.0058	$228.01	$228.00	$228.00
Purchase #6	$21.62	3.474%	$22.3711	$22.37	$22.35	$22.40
Purchase #7	$206.71	7.642%	$222.5068	$222.51	$222.50	$222.50
7 purchase totals =	$830.83		$907.8859	$907.89	$907.80	$907.90