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	$141.62	5.528%	$149.4488	$149.45	$149.45	$149.40
Purchase #2	$171.93	4.436%	$179.5568	$179.56	$179.55	$179.60
Purchase #3	$90.80	13.825%	$103.3531	$103.35	$103.35	$103.40
Purchase #4	$172.78	13.778%	$196.5856	$196.59	$196.60	$196.60
Purchase #5	$240.42	9.526%	$263.3224	$263.32	$263.30	$263.30
Purchase #6	$79.77	12.872%	$90.038	$90.04	$90.05	$90.00
Purchase #7	$21.86	9.830%	$24.0088	$24.01	$24.00	$24.00
7 purchase totals =	$919.18		$1,006.3135	$1,006.32	$1,006.30	$1,006.30