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	$184.91	4.297%	$192.8556	$192.86	$192.85	$192.90
Purchase #2	$21.39	9.191%	$23.356	$23.36	$23.35	$23.40
Purchase #3	$38.35	6.706%	$40.9218	$40.92	$40.90	$40.90
Purchase #4	$40.45	4.653%	$42.3321	$42.33	$42.35	$42.30
Purchase #5	$135.71	6.374%	$144.3602	$144.36	$144.35	$144.40
Purchase #6	$100.37	5.380%	$105.7699	$105.77	$105.75	$105.80
Purchase #7	$113.83	5.258%	$119.8152	$119.82	$119.80	$119.80
7 purchase totals =	$635.01		$669.4108	$669.42	$669.35	$669.50