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	$64.58	9.184%	$70.511	$70.51	$70.50	$70.50
Purchase #2	$119.99	3.285%	$123.9317	$123.93	$123.95	$123.90
Purchase #3	$46.45	8.591%	$50.4405	$50.44	$50.45	$50.40
Purchase #4	$56.86	4.227%	$59.2635	$59.26	$59.25	$59.30
Purchase #5	$77.94	10.585%	$86.1899	$86.19	$86.20	$86.20
Purchase #6	$21.80	3.127%	$22.4817	$22.48	$22.50	$22.50
Purchase #7	$53.89	5.127%	$56.6529	$56.65	$56.65	$56.70
7 purchase totals =	$441.51		$469.4712	$469.46	$469.50	$469.50