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	$163.38	8.293%	$176.9291	$176.93	$176.95	$176.90
Purchase #2	$215.93	3.790%	$224.1137	$224.11	$224.10	$224.10
Purchase #3	$244.95	5.526%	$258.4859	$258.49	$258.50	$258.50
Purchase #4	$159.35	9.521%	$174.5217	$174.52	$174.50	$174.50
Purchase #5	$120.31	8.356%	$130.3631	$130.36	$130.35	$130.40
Purchase #6	$61.41	10.104%	$67.6149	$67.61	$67.60	$67.60
Purchase #7	$56.47	6.158%	$59.9474	$59.95	$59.95	$59.90
7 purchase totals =	$1,021.80		$1,091.9758	$1,091.97	$1,091.95	$1,091.90