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	$214.63	3.847%	$222.8868	$222.89	$222.90	$222.90
Purchase #2	$186.62	12.448%	$209.8505	$209.85	$209.85	$209.90
Purchase #3	$160.45	11.137%	$178.3193	$178.32	$178.30	$178.30
Purchase #4	$166.84	10.301%	$184.0262	$184.03	$184.05	$184.00
Purchase #5	$75.61	8.814%	$82.2743	$82.27	$82.25	$82.30
Purchase #6	$210.95	9.745%	$231.5071	$231.51	$231.50	$231.50
Purchase #7	$95.62	5.140%	$100.5349	$100.53	$100.55	$100.50
7 purchase totals =	$1,110.72		$1,209.3991	$1,209.40	$1,209.40	$1,209.40