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	$226.25	4.122%	$235.576	$235.58	$235.60	$235.60
Purchase #2	$156.57	4.575%	$163.7331	$163.73	$163.75	$163.70
Purchase #3	$63.74	13.665%	$72.4501	$72.45	$72.45	$72.50
Purchase #4	$79.72	13.409%	$90.4097	$90.41	$90.40	$90.40
Purchase #5	$101.45	3.444%	$104.9439	$104.94	$104.95	$104.90
Purchase #6	$39.84	7.546%	$42.8463	$42.85	$42.85	$42.80
Purchase #7	$103.56	10.533%	$114.468	$114.47	$114.45	$114.50
7 purchase totals =	$771.13		$824.4271	$824.43	$824.45	$824.40