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	$244.50	5.761%	$258.5856	$258.59	$258.60	$258.60
Purchase #2	$33.64	12.196%	$37.7427	$37.74	$37.75	$37.70
Purchase #3	$145.71	12.846%	$164.4279	$164.43	$164.45	$164.40
Purchase #4	$179.80	6.755%	$191.9455	$191.95	$191.95	$191.90
Purchase #5	$166.41	8.410%	$180.4051	$180.41	$180.40	$180.40
Purchase #6	$215.46	6.207%	$228.8336	$228.83	$228.85	$228.80
Purchase #7	$38.29	7.647%	$41.218	$41.22	$41.20	$41.20
7 purchase totals =	$1,023.81		$1,103.1584	$1,103.17	$1,103.20	$1,103.00