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	$200.35	11.256%	$222.9014	$222.90	$222.90	$222.90
Purchase #2	$240.38	10.386%	$265.3459	$265.35	$265.35	$265.30
Purchase #3	$113.85	4.378%	$118.8344	$118.83	$118.85	$118.80
Purchase #4	$176.29	4.315%	$183.8969	$183.90	$183.90	$183.90
Purchase #5	$147.75	5.294%	$155.5719	$155.57	$155.55	$155.60
Purchase #6	$161.83	6.190%	$171.8473	$171.85	$171.85	$171.80
Purchase #7	$181.59	5.709%	$191.957	$191.96	$191.95	$192.00
7 purchase totals =	$1,222.04		$1,310.3548	$1,310.36	$1,310.35	$1,310.30