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	$89.63	6.705%	$95.6397	$95.64	$95.65	$95.60
Purchase #2	$168.74	12.864%	$190.4467	$190.45	$190.45	$190.40
Purchase #3	$129.70	9.686%	$142.2627	$142.26	$142.25	$142.30
Purchase #4	$246.90	10.462%	$272.7307	$272.73	$272.75	$272.70
Purchase #5	$173.57	8.290%	$187.959	$187.96	$187.95	$188.00
Purchase #6	$221.46	7.535%	$238.147	$238.15	$238.15	$238.10
Purchase #7	$91.96	9.330%	$100.5399	$100.54	$100.55	$100.50
7 purchase totals =	$1,121.96		$1,227.7257	$1,227.73	$1,227.75	$1,227.60