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	$158.63	3.456%	$164.1123	$164.11	$164.10	$164.10
Purchase #2	$116.33	6.369%	$123.7391	$123.74	$123.75	$123.70
Purchase #3	$131.93	8.378%	$142.9831	$142.98	$143.00	$143.00
Purchase #4	$183.77	9.222%	$200.7173	$200.72	$200.70	$200.70
Purchase #5	$126.75	7.658%	$136.4565	$136.46	$136.45	$136.50
Purchase #6	$128.45	7.250%	$137.7626	$137.76	$137.75	$137.80
Purchase #7	$53.86	12.874%	$60.7939	$60.79	$60.80	$60.80
7 purchase totals =	$899.72		$966.5648	$966.56	$966.55	$966.60