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	$194.64	10.782%	$215.6261	$215.63	$215.65	$215.60
Purchase #2	$74.93	10.348%	$82.6838	$82.68	$82.70	$82.70
Purchase #3	$126.92	10.279%	$139.9661	$139.97	$139.95	$140.00
Purchase #4	$56.73	8.284%	$61.4295	$61.43	$61.45	$61.40
Purchase #5	$167.78	12.579%	$188.885	$188.89	$188.90	$188.90
Purchase #6	$239.77	11.324%	$266.9216	$266.92	$266.90	$266.90
Purchase #7	$216.88	12.778%	$244.5929	$244.59	$244.60	$244.60
7 purchase totals =	$1,077.65		$1,200.1050	$1,200.11	$1,200.15	$1,200.10