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	$181.82	4.691%	$190.3492	$190.35	$190.35	$190.30
Purchase #2	$230.47	10.441%	$254.5334	$254.53	$254.55	$254.50
Purchase #3	$80.39	11.752%	$89.8374	$89.84	$89.85	$89.80
Purchase #4	$221.86	11.232%	$246.7793	$246.78	$246.80	$246.80
Purchase #5	$94.99	4.144%	$98.9264	$98.93	$98.95	$98.90
Purchase #6	$101.64	9.730%	$111.5296	$111.53	$111.55	$111.50
Purchase #7	$35.31	5.420%	$37.2238	$37.22	$37.20	$37.20
7 purchase totals =	$946.48		$1,029.1791	$1,029.18	$1,029.25	$1,029.00