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	$183.36	7.757%	$197.5832	$197.58	$197.60	$197.60
Purchase #2	$59.47	4.165%	$61.9469	$61.95	$61.95	$61.90
Purchase #3	$38.49	9.241%	$42.0469	$42.05	$42.05	$42.00
Purchase #4	$150.40	3.747%	$156.0355	$156.04	$156.05	$156.00
Purchase #5	$104.65	6.146%	$111.0818	$111.08	$111.10	$111.10
Purchase #6	$88.57	3.832%	$91.964	$91.96	$91.95	$92.00
Purchase #7	$189.77	8.188%	$205.3084	$205.31	$205.30	$205.30
7 purchase totals =	$814.71		$865.9667	$865.97	$866.00	$865.90