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	$236.43	3.410%	$244.4923	$244.49	$244.50	$244.50
Purchase #2	$107.83	4.644%	$112.8376	$112.84	$112.85	$112.80
Purchase #3	$162.33	5.545%	$171.3312	$171.33	$171.35	$171.30
Purchase #4	$184.59	3.394%	$190.855	$190.86	$190.85	$190.90
Purchase #5	$43.52	5.287%	$45.8209	$45.82	$45.80	$45.80
Purchase #6	$115.36	7.169%	$123.6302	$123.63	$123.65	$123.60
Purchase #7	$6.58	3.263%	$6.7947	$6.79	$6.80	$6.80
7 purchase totals =	$856.64		$895.7619	$895.76	$895.80	$895.70