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	$140.72	8.574%	$152.7853	$152.79	$152.80	$152.80
Purchase #2	$69.52	11.620%	$77.5982	$77.60	$77.60	$77.60
Purchase #3	$123.94	8.362%	$134.3039	$134.30	$134.30	$134.30
Purchase #4	$245.62	6.115%	$260.6397	$260.64	$260.65	$260.60
Purchase #5	$83.86	7.618%	$90.2485	$90.25	$90.25	$90.20
Purchase #6	$193.78	6.731%	$206.8233	$206.82	$206.80	$206.80
Purchase #7	$73.93	10.305%	$81.5485	$81.55	$81.55	$81.50
7 purchase totals =	$931.37		$1,003.9474	$1,003.95	$1,003.95	$1,003.80