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	$53.43	4.495%	$55.8317	$55.83	$55.85	$55.80
Purchase #2	$237.89	8.817%	$258.8648	$258.86	$258.85	$258.90
Purchase #3	$166.45	7.524%	$178.9737	$178.97	$178.95	$179.00
Purchase #4	$165.74	10.730%	$183.5239	$183.52	$183.50	$183.50
Purchase #5	$77.98	10.557%	$86.2123	$86.21	$86.20	$86.20
Purchase #6	$143.48	6.280%	$152.4905	$152.49	$152.50	$152.50
Purchase #7	$147.59	3.566%	$152.8531	$152.85	$152.85	$152.90
7 purchase totals =	$992.56		$1,068.7500	$1,068.73	$1,068.70	$1,068.80