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	$47.72	13.590%	$54.2051	$54.21	$54.20	$54.20
Purchase #2	$198.93	6.847%	$212.5507	$212.55	$212.55	$212.60
Purchase #3	$194.87	13.567%	$221.308	$221.31	$221.30	$221.30
Purchase #4	$93.55	7.731%	$100.7824	$100.78	$100.80	$100.80
Purchase #5	$126.98	13.718%	$144.3991	$144.40	$144.40	$144.40
Purchase #6	$234.30	13.469%	$265.8579	$265.86	$265.85	$265.90
Purchase #7	$21.69	13.308%	$24.5765	$24.58	$24.60	$24.60
7 purchase totals =	$918.04		$1,023.6797	$1,023.69	$1,023.70	$1,023.80