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	$104.69	11.244%	$116.4613	$116.46	$116.45	$116.50
Purchase #2	$88.32	8.714%	$96.0162	$96.02	$96.00	$96.00
Purchase #3	$132.28	12.191%	$148.4063	$148.41	$148.40	$148.40
Purchase #4	$67.27	11.413%	$74.9475	$74.95	$74.95	$74.90
Purchase #5	$36.36	10.396%	$40.14	$40.14	$40.15	$40.10
Purchase #6	$34.30	13.506%	$38.9326	$38.93	$38.95	$38.90
Purchase #7	$234.39	9.444%	$256.5258	$256.53	$256.55	$256.50
7 purchase totals =	$697.61		$771.4297	$771.44	$771.45	$771.30