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	$33.87	4.600%	$35.428	$35.43	$35.45	$35.40
Purchase #2	$182.51	6.309%	$194.0246	$194.02	$194.00	$194.00
Purchase #3	$124.77	6.499%	$132.8788	$132.88	$132.90	$132.90
Purchase #4	$54.54	8.493%	$59.1721	$59.17	$59.15	$59.20
Purchase #5	$53.66	3.712%	$55.6519	$55.65	$55.65	$55.70
Purchase #6	$33.37	11.160%	$37.0941	$37.09	$37.10	$37.10
Purchase #7	$57.70	3.351%	$59.6335	$59.63	$59.65	$59.60
7 purchase totals =	$540.42		$573.8830	$573.87	$573.90	$573.90