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	$132.63	9.588%	$145.3466	$145.35	$145.35	$145.30
Purchase #2	$222.59	9.800%	$244.4038	$244.40	$244.40	$244.40
Purchase #3	$132.88	6.469%	$141.476	$141.48	$141.50	$141.50
Purchase #4	$222.96	10.812%	$247.0664	$247.07	$247.05	$247.10
Purchase #5	$178.40	10.180%	$196.5611	$196.56	$196.55	$196.60
Purchase #6	$84.55	13.570%	$96.0234	$96.02	$96.00	$96.00
Purchase #7	$42.76	6.618%	$45.5899	$45.59	$45.60	$45.60
7 purchase totals =	$1,016.77		$1,116.4672	$1,116.47	$1,116.45	$1,116.50