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	$217.58	5.318%	$229.1509	$229.15	$229.15	$229.20
Purchase #2	$40.98	4.759%	$42.9302	$42.93	$42.95	$42.90
Purchase #3	$65.46	3.646%	$67.8467	$67.85	$67.85	$67.80
Purchase #4	$57.61	8.173%	$62.3185	$62.32	$62.30	$62.30
Purchase #5	$148.67	3.438%	$153.7813	$153.78	$153.80	$153.80
Purchase #6	$165.90	7.309%	$178.0256	$178.03	$178.05	$178.00
Purchase #7	$246.38	9.742%	$270.3823	$270.38	$270.40	$270.40
7 purchase totals =	$942.58		$1,004.4355	$1,004.44	$1,004.50	$1,004.40