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	$206.54	13.874%	$235.1954	$235.20	$235.20	$235.20
Purchase #2	$188.63	4.179%	$196.5128	$196.51	$196.50	$196.50
Purchase #3	$157.33	3.257%	$162.4542	$162.45	$162.45	$162.50
Purchase #4	$91.46	9.738%	$100.3664	$100.37	$100.35	$100.40
Purchase #5	$146.62	5.542%	$154.7457	$154.75	$154.75	$154.70
Purchase #6	$46.67	13.417%	$52.9317	$52.93	$52.95	$52.90
Purchase #7	$221.34	9.387%	$242.1172	$242.12	$242.10	$242.10
7 purchase totals =	$1,058.59		$1,144.3234	$1,144.33	$1,144.30	$1,144.30