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	$212.89	4.689%	$222.8724	$222.87	$222.85	$222.90
Purchase #2	$122.90	4.482%	$128.4084	$128.41	$128.40	$128.40
Purchase #3	$208.43	10.398%	$230.1026	$230.10	$230.10	$230.10
Purchase #4	$8.78	10.696%	$9.7191	$9.72	$9.70	$9.70
Purchase #5	$169.71	7.187%	$181.9071	$181.91	$181.90	$181.90
Purchase #6	$69.99	12.429%	$78.6891	$78.69	$78.70	$78.70
Purchase #7	$150.39	12.122%	$168.6203	$168.62	$168.60	$168.60
7 purchase totals =	$943.09		$1,020.3190	$1,020.32	$1,020.25	$1,020.30