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	$211.62	5.338%	$222.9163	$222.92	$222.90	$222.90
Purchase #2	$56.61	9.637%	$62.0655	$62.07	$62.05	$62.10
Purchase #3	$170.96	3.851%	$177.5437	$177.54	$177.55	$177.50
Purchase #4	$194.37	9.854%	$213.5232	$213.52	$213.50	$213.50
Purchase #5	$243.59	12.392%	$273.7757	$273.78	$273.80	$273.80
Purchase #6	$145.96	3.131%	$150.53	$150.53	$150.55	$150.50
Purchase #7	$144.53	4.253%	$150.6769	$150.68	$150.70	$150.70
7 purchase totals =	$1,167.64		$1,251.0313	$1,251.04	$1,251.05	$1,251.00