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	$106.97	6.441%	$113.8599	$113.86	$113.85	$113.90
Purchase #2	$76.72	7.549%	$82.5116	$82.51	$82.50	$82.50
Purchase #3	$102.96	11.579%	$114.8817	$114.88	$114.90	$114.90
Purchase #4	$119.85	9.413%	$131.1315	$131.13	$131.15	$131.10
Purchase #5	$246.61	4.821%	$258.4991	$258.50	$258.50	$258.50
Purchase #6	$170.88	9.362%	$186.8778	$186.88	$186.90	$186.90
Purchase #7	$190.80	3.198%	$196.9018	$196.90	$196.90	$196.90
7 purchase totals =	$1,014.79		$1,084.6634	$1,084.66	$1,084.70	$1,084.70