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	$34.32	9.482%	$37.5742	$37.57	$37.55	$37.60
Purchase #2	$88.71	13.608%	$100.7817	$100.78	$100.80	$100.80
Purchase #3	$243.91	3.524%	$252.5054	$252.51	$252.50	$252.50
Purchase #4	$137.66	13.534%	$156.2909	$156.29	$156.30	$156.30
Purchase #5	$181.86	7.226%	$195.0012	$195.00	$195.00	$195.00
Purchase #6	$54.52	9.630%	$59.7703	$59.77	$59.75	$59.80
Purchase #7	$221.93	6.481%	$236.3133	$236.31	$236.30	$236.30
7 purchase totals =	$962.91		$1,038.2370	$1,038.23	$1,038.20	$1,038.30