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	$92.96	8.251%	$100.6301	$100.63	$100.65	$100.60
Purchase #2	$191.76	13.472%	$217.5939	$217.59	$217.60	$217.60
Purchase #3	$114.71	10.470%	$126.7201	$126.72	$126.70	$126.70
Purchase #4	$23.37	10.356%	$25.7902	$25.79	$25.80	$25.80
Purchase #5	$210.59	5.583%	$222.3472	$222.35	$222.35	$222.30
Purchase #6	$224.82	6.375%	$239.1523	$239.15	$239.15	$239.20
Purchase #7	$125.43	12.843%	$141.539	$141.54	$141.55	$141.50
7 purchase totals =	$983.64		$1,073.7728	$1,073.77	$1,073.80	$1,073.70