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	$83.94	3.336%	$86.7402	$86.74	$86.75	$86.70
Purchase #2	$71.91	13.345%	$81.5064	$81.51	$81.50	$81.50
Purchase #3	$177.53	13.127%	$200.8344	$200.83	$200.85	$200.80
Purchase #4	$144.87	6.627%	$154.4705	$154.47	$154.45	$154.50
Purchase #5	$243.59	13.658%	$276.8595	$276.86	$276.85	$276.90
Purchase #6	$72.86	9.532%	$79.805	$79.81	$79.80	$79.80
Purchase #7	$157.80	8.692%	$171.516	$171.52	$171.50	$171.50
7 purchase totals =	$952.50		$1,051.7320	$1,051.74	$1,051.70	$1,051.70