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	$174.49	8.580%	$189.4612	$189.46	$189.45	$189.50
Purchase #2	$96.41	8.550%	$104.6531	$104.65	$104.65	$104.70
Purchase #3	$81.76	5.770%	$86.4776	$86.48	$86.50	$86.50
Purchase #4	$158.93	3.736%	$164.8676	$164.87	$164.85	$164.90
Purchase #5	$92.50	11.817%	$103.4307	$103.43	$103.45	$103.40
Purchase #6	$136.42	6.182%	$144.8535	$144.85	$144.85	$144.90
Purchase #7	$73.31	5.697%	$77.4865	$77.49	$77.50	$77.50
7 purchase totals =	$813.82		$871.2302	$871.23	$871.25	$871.40