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	$183.54	4.615%	$192.0104	$192.01	$192.00	$192.00
Purchase #2	$132.70	4.815%	$139.0895	$139.09	$139.10	$139.10
Purchase #3	$42.50	6.495%	$45.2604	$45.26	$45.25	$45.30
Purchase #4	$233.91	10.599%	$258.7021	$258.70	$258.70	$258.70
Purchase #5	$92.48	9.773%	$101.5181	$101.52	$101.50	$101.50
Purchase #6	$236.57	5.525%	$249.6405	$249.64	$249.65	$249.60
Purchase #7	$182.90	7.258%	$196.1749	$196.17	$196.15	$196.20
7 purchase totals =	$1,104.60		$1,182.3959	$1,182.39	$1,182.35	$1,182.40