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	$98.71	5.791%	$104.4263	$104.43	$104.45	$104.40
Purchase #2	$136.75	12.782%	$154.2294	$154.23	$154.25	$154.20
Purchase #3	$75.40	9.446%	$82.5223	$82.52	$82.50	$82.50
Purchase #4	$221.94	10.653%	$245.5833	$245.58	$245.60	$245.60
Purchase #5	$64.25	12.598%	$72.3442	$72.34	$72.35	$72.30
Purchase #6	$199.57	4.770%	$209.0895	$209.09	$209.10	$209.10
Purchase #7	$141.38	5.677%	$149.4061	$149.41	$149.40	$149.40
7 purchase totals =	$938.00		$1,017.6011	$1,017.60	$1,017.65	$1,017.50