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	$52.98	7.542%	$56.9758	$56.98	$57.00	$57.00
Purchase #2	$243.74	3.353%	$251.9126	$251.91	$251.90	$251.90
Purchase #3	$71.85	3.336%	$74.2469	$74.25	$74.25	$74.20
Purchase #4	$219.98	7.477%	$236.4279	$236.43	$236.45	$236.40
Purchase #5	$138.41	10.334%	$152.7133	$152.71	$152.70	$152.70
Purchase #6	$92.39	12.156%	$103.6209	$103.62	$103.60	$103.60
Purchase #7	$126.51	11.315%	$140.8246	$140.82	$140.80	$140.80
7 purchase totals =	$945.86		$1,016.7220	$1,016.72	$1,016.70	$1,016.60