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	$227.81	4.850%	$238.8588	$238.86	$238.85	$238.90
Purchase #2	$85.39	9.612%	$93.5977	$93.60	$93.60	$93.60
Purchase #3	$185.77	3.518%	$192.3054	$192.31	$192.30	$192.30
Purchase #4	$38.86	9.415%	$42.5187	$42.52	$42.50	$42.50
Purchase #5	$179.71	3.624%	$186.2227	$186.22	$186.20	$186.20
Purchase #6	$80.34	11.459%	$89.5462	$89.55	$89.55	$89.50
Purchase #7	$231.37	12.238%	$259.6851	$259.69	$259.70	$259.70
7 purchase totals =	$1,029.25		$1,102.7346	$1,102.75	$1,102.70	$1,102.70