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	$135.64	3.325%	$140.15	$140.15	$140.15	$140.20
Purchase #2	$123.25	11.579%	$137.5211	$137.52	$137.50	$137.50
Purchase #3	$113.76	5.275%	$119.7608	$119.76	$119.75	$119.80
Purchase #4	$97.46	13.138%	$110.2643	$110.26	$110.25	$110.30
Purchase #5	$223.97	11.750%	$250.2865	$250.29	$250.30	$250.30
Purchase #6	$236.90	10.314%	$261.3339	$261.33	$261.35	$261.30
Purchase #7	$103.69	4.727%	$108.5914	$108.59	$108.60	$108.60
7 purchase totals =	$1,034.67		$1,127.9080	$1,127.90	$1,127.90	$1,128.00