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	$171.42	8.193%	$185.4644	$185.46	$185.45	$185.50
Purchase #2	$85.71	11.259%	$95.3601	$95.36	$95.35	$95.40
Purchase #3	$103.26	7.700%	$111.211	$111.21	$111.20	$111.20
Purchase #4	$73.94	11.673%	$82.571	$82.57	$82.55	$82.60
Purchase #5	$52.86	12.686%	$59.5658	$59.57	$59.55	$59.60
Purchase #6	$120.86	9.312%	$132.1145	$132.11	$132.10	$132.10
Purchase #7	$54.95	3.274%	$56.7491	$56.75	$56.75	$56.70
7 purchase totals =	$663.00		$723.0359	$723.03	$722.95	$723.10