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	$48.33	12.513%	$54.3775	$54.38	$54.40	$54.40
Purchase #2	$174.26	10.483%	$192.5277	$192.53	$192.55	$192.50
Purchase #3	$187.80	13.581%	$213.3051	$213.31	$213.30	$213.30
Purchase #4	$218.79	11.273%	$243.4542	$243.45	$243.45	$243.50
Purchase #5	$30.62	9.182%	$33.4315	$33.43	$33.45	$33.40
Purchase #6	$182.53	5.209%	$192.038	$192.04	$192.05	$192.00
Purchase #7	$162.96	5.613%	$172.1069	$172.11	$172.10	$172.10
7 purchase totals =	$1,005.29		$1,101.2409	$1,101.25	$1,101.30	$1,101.20