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	$20.44	7.323%	$21.9368	$21.94	$21.95	$21.90
Purchase #2	$37.51	7.179%	$40.2028	$40.20	$40.20	$40.20
Purchase #3	$144.56	12.711%	$162.935	$162.94	$162.95	$162.90
Purchase #4	$132.83	7.198%	$142.3911	$142.39	$142.40	$142.40
Purchase #5	$12.47	6.570%	$13.2893	$13.29	$13.30	$13.30
Purchase #6	$33.79	8.618%	$36.702	$36.70	$36.70	$36.70
Purchase #7	$206.60	5.770%	$218.5208	$218.52	$218.50	$218.50
7 purchase totals =	$588.20		$635.9778	$635.98	$636.00	$635.90