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	$54.64	8.536%	$59.3041	$59.30	$59.30	$59.30
Purchase #2	$237.49	13.179%	$268.7888	$268.79	$268.80	$268.80
Purchase #3	$152.87	3.522%	$158.2541	$158.25	$158.25	$158.30
Purchase #4	$29.63	11.282%	$32.9729	$32.97	$32.95	$33.00
Purchase #5	$170.93	4.142%	$178.0099	$178.01	$178.00	$178.00
Purchase #6	$241.54	13.744%	$274.7373	$274.74	$274.75	$274.70
Purchase #7	$166.47	9.253%	$181.8735	$181.87	$181.85	$181.90
7 purchase totals =	$1,053.57		$1,153.9406	$1,153.93	$1,153.90	$1,154.00