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	$52.85	5.406%	$55.7071	$55.71	$55.70	$55.70
Purchase #2	$52.97	13.504%	$60.1231	$60.12	$60.10	$60.10
Purchase #3	$136.77	13.252%	$154.8948	$154.89	$154.90	$154.90
Purchase #4	$42.74	7.161%	$45.8006	$45.80	$45.80	$45.80
Purchase #5	$79.31	3.538%	$82.116	$82.12	$82.10	$82.10
Purchase #6	$180.83	6.558%	$192.6888	$192.69	$192.70	$192.70
Purchase #7	$189.88	3.304%	$196.1536	$196.15	$196.15	$196.20
7 purchase totals =	$735.35		$787.4840	$787.48	$787.45	$787.50