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	$141.52	6.521%	$150.7485	$150.75	$150.75	$150.70
Purchase #2	$65.91	8.503%	$71.5143	$71.51	$71.50	$71.50
Purchase #3	$50.98	5.758%	$53.9154	$53.92	$53.90	$53.90
Purchase #4	$55.37	10.684%	$61.2857	$61.29	$61.30	$61.30
Purchase #5	$98.77	8.751%	$107.4134	$107.41	$107.40	$107.40
Purchase #6	$118.86	3.805%	$123.3826	$123.38	$123.40	$123.40
Purchase #7	$169.36	13.105%	$191.5546	$191.55	$191.55	$191.60
7 purchase totals =	$700.77		$759.8145	$759.81	$759.80	$759.80