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	$97.32	9.868%	$106.9235	$106.92	$106.90	$106.90
Purchase #2	$126.77	8.507%	$137.5543	$137.55	$137.55	$137.60
Purchase #3	$89.39	6.170%	$94.9054	$94.91	$94.90	$94.90
Purchase #4	$104.42	10.697%	$115.5898	$115.59	$115.60	$115.60
Purchase #5	$39.79	8.680%	$43.2438	$43.24	$43.25	$43.20
Purchase #6	$198.40	3.746%	$205.8321	$205.83	$205.85	$205.80
Purchase #7	$48.68	11.180%	$54.1224	$54.12	$54.10	$54.10
7 purchase totals =	$704.77		$758.1713	$758.16	$758.15	$758.10