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	$75.89	11.405%	$84.5453	$84.55	$84.55	$84.50
Purchase #2	$190.38	10.759%	$210.863	$210.86	$210.85	$210.90
Purchase #3	$194.33	4.722%	$203.5063	$203.51	$203.50	$203.50
Purchase #4	$55.27	7.273%	$59.2898	$59.29	$59.30	$59.30
Purchase #5	$238.70	6.406%	$253.9911	$253.99	$254.00	$254.00
Purchase #6	$182.93	7.544%	$196.7302	$196.73	$196.75	$196.70
Purchase #7	$146.67	6.579%	$156.3194	$156.32	$156.30	$156.30
7 purchase totals =	$1,084.17		$1,165.2451	$1,165.25	$1,165.25	$1,165.20