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	$119.69	7.723%	$128.9337	$128.93	$128.95	$128.90
Purchase #2	$141.91	7.680%	$152.8087	$152.81	$152.80	$152.80
Purchase #3	$177.79	7.765%	$191.5954	$191.60	$191.60	$191.60
Purchase #4	$72.40	11.389%	$80.6456	$80.65	$80.65	$80.60
Purchase #5	$232.94	9.482%	$255.0274	$255.03	$255.05	$255.00
Purchase #6	$216.69	13.124%	$245.1284	$245.13	$245.15	$245.10
Purchase #7	$231.59	5.759%	$244.9273	$244.93	$244.95	$244.90
7 purchase totals =	$1,193.01		$1,299.0665	$1,299.08	$1,299.15	$1,298.90