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	$48.66	10.201%	$53.6238	$53.62	$53.60	$53.60
Purchase #2	$131.46	4.490%	$137.3626	$137.36	$137.35	$137.40
Purchase #3	$156.95	4.792%	$164.471	$164.47	$164.45	$164.50
Purchase #4	$198.33	4.233%	$206.7253	$206.73	$206.75	$206.70
Purchase #5	$122.75	4.587%	$128.3805	$128.38	$128.40	$128.40
Purchase #6	$248.27	7.275%	$266.3316	$266.33	$266.35	$266.30
Purchase #7	$127.50	9.239%	$139.2797	$139.28	$139.30	$139.30
7 purchase totals =	$1,033.92		$1,096.1745	$1,096.17	$1,096.20	$1,096.20