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	$54.83	12.817%	$61.8576	$61.86	$61.85	$61.90
Purchase #2	$92.77	11.497%	$103.4358	$103.44	$103.45	$103.40
Purchase #3	$126.48	3.753%	$131.2268	$131.23	$131.25	$131.20
Purchase #4	$83.58	13.498%	$94.8616	$94.86	$94.85	$94.90
Purchase #5	$243.99	13.251%	$276.3211	$276.32	$276.30	$276.30
Purchase #6	$99.72	8.789%	$108.4844	$108.48	$108.50	$108.50
Purchase #7	$155.50	5.679%	$164.3308	$164.33	$164.35	$164.30
7 purchase totals =	$856.87		$940.5181	$940.52	$940.55	$940.50