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	$116.85	9.705%	$128.1903	$128.19	$128.20	$128.20
Purchase #2	$179.62	4.398%	$187.5197	$187.52	$187.50	$187.50
Purchase #3	$171.61	3.233%	$177.1582	$177.16	$177.15	$177.20
Purchase #4	$96.44	13.540%	$109.498	$109.50	$109.50	$109.50
Purchase #5	$188.58	5.485%	$198.9236	$198.92	$198.90	$198.90
Purchase #6	$115.79	13.863%	$131.842	$131.84	$131.85	$131.80
Purchase #7	$77.63	7.822%	$83.7022	$83.70	$83.70	$83.70
7 purchase totals =	$946.52		$1,016.8340	$1,016.83	$1,016.80	$1,016.80