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	$141.45	5.162%	$148.7516	$148.75	$148.75	$148.80
Purchase #2	$11.33	4.323%	$11.8198	$11.82	$11.80	$11.80
Purchase #3	$204.66	6.621%	$218.2105	$218.21	$218.20	$218.20
Purchase #4	$172.83	13.655%	$196.4299	$196.43	$196.45	$196.40
Purchase #5	$17.81	11.632%	$19.8817	$19.88	$19.90	$19.90
Purchase #6	$205.80	10.658%	$227.7342	$227.73	$227.75	$227.70
Purchase #7	$30.37	8.310%	$32.8937	$32.89	$32.90	$32.90
7 purchase totals =	$784.25		$855.7214	$855.71	$855.75	$855.70