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	$215.74	10.714%	$238.8544	$238.85	$238.85	$238.90
Purchase #2	$143.43	3.398%	$148.3038	$148.30	$148.30	$148.30
Purchase #3	$181.96	10.172%	$200.469	$200.47	$200.45	$200.50
Purchase #4	$147.35	10.362%	$162.6184	$162.62	$162.60	$162.60
Purchase #5	$245.63	5.366%	$258.8105	$258.81	$258.80	$258.80
Purchase #6	$115.33	7.155%	$123.5819	$123.58	$123.60	$123.60
Purchase #7	$7.95	7.380%	$8.5367	$8.54	$8.55	$8.50
7 purchase totals =	$1,057.39		$1,141.1747	$1,141.17	$1,141.15	$1,141.20