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	$5.44	3.526%	$5.6318	$5.63	$5.65	$5.60
Purchase #2	$249.66	3.604%	$258.6577	$258.66	$258.65	$258.70
Purchase #3	$165.49	12.641%	$186.4096	$186.41	$186.40	$186.40
Purchase #4	$182.48	9.871%	$200.4926	$200.49	$200.50	$200.50
Purchase #5	$100.58	11.234%	$111.8792	$111.88	$111.90	$111.90
Purchase #6	$67.62	13.231%	$76.5668	$76.57	$76.55	$76.60
Purchase #7	$129.75	5.692%	$137.1354	$137.14	$137.15	$137.10
7 purchase totals =	$901.02		$976.7731	$976.78	$976.80	$976.80