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	$58.52	5.830%	$61.9317	$61.93	$61.95	$61.90
Purchase #2	$221.40	11.778%	$247.4765	$247.48	$247.50	$247.50
Purchase #3	$84.29	6.561%	$89.8203	$89.82	$89.80	$89.80
Purchase #4	$197.86	10.483%	$218.6017	$218.60	$218.60	$218.60
Purchase #5	$131.93	10.228%	$145.4238	$145.42	$145.40	$145.40
Purchase #6	$23.91	12.167%	$26.8191	$26.82	$26.80	$26.80
Purchase #7	$201.91	12.210%	$226.5632	$226.56	$226.55	$226.60
7 purchase totals =	$919.82		$1,016.6363	$1,016.63	$1,016.60	$1,016.60