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	$86.33	11.126%	$95.9351	$95.94	$95.95	$95.90
Purchase #2	$144.84	3.438%	$149.8196	$149.82	$149.80	$149.80
Purchase #3	$82.93	7.832%	$89.4251	$89.43	$89.45	$89.40
Purchase #4	$213.51	7.534%	$229.5958	$229.60	$229.60	$229.60
Purchase #5	$116.55	11.871%	$130.3857	$130.39	$130.40	$130.40
Purchase #6	$193.60	5.669%	$204.5752	$204.58	$204.60	$204.60
Purchase #7	$128.31	9.722%	$140.7843	$140.78	$140.80	$140.80
7 purchase totals =	$966.07		$1,040.5208	$1,040.54	$1,040.60	$1,040.50