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	$175.67	5.795%	$185.8501	$185.85	$185.85	$185.90
Purchase #2	$29.46	11.602%	$32.8779	$32.88	$32.90	$32.90
Purchase #3	$25.81	13.443%	$29.2796	$29.28	$29.30	$29.30
Purchase #4	$152.38	10.510%	$168.3951	$168.40	$168.40	$168.40
Purchase #5	$55.93	10.818%	$61.9805	$61.98	$62.00	$62.00
Purchase #6	$103.37	11.395%	$115.149	$115.15	$115.15	$115.10
Purchase #7	$126.74	11.119%	$140.8322	$140.83	$140.85	$140.80
7 purchase totals =	$669.36		$734.3644	$734.37	$734.45	$734.40