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	$145.49	9.591%	$159.4439	$159.44	$159.45	$159.40
Purchase #2	$121.33	5.423%	$127.9097	$127.91	$127.90	$127.90
Purchase #3	$176.79	3.267%	$182.5657	$182.57	$182.55	$182.60
Purchase #4	$161.95	7.444%	$174.0056	$174.01	$174.00	$174.00
Purchase #5	$28.70	9.227%	$31.3481	$31.35	$31.35	$31.30
Purchase #6	$96.51	9.282%	$105.4681	$105.47	$105.45	$105.50
Purchase #7	$179.97	11.633%	$200.9059	$200.91	$200.90	$200.90
7 purchase totals =	$910.74		$981.6470	$981.66	$981.60	$981.60