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	$134.52	9.306%	$147.0384	$147.04	$147.05	$147.00
Purchase #2	$137.40	13.400%	$155.8116	$155.81	$155.80	$155.80
Purchase #3	$100.48	9.399%	$109.9241	$109.92	$109.90	$109.90
Purchase #4	$44.59	9.423%	$48.7917	$48.79	$48.80	$48.80
Purchase #5	$228.40	5.490%	$240.9392	$240.94	$240.95	$240.90
Purchase #6	$139.60	8.107%	$150.9174	$150.92	$150.90	$150.90
Purchase #7	$155.81	4.666%	$163.0801	$163.08	$163.10	$163.10
7 purchase totals =	$940.80		$1,016.5025	$1,016.50	$1,016.50	$1,016.40