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	$52.50	5.120%	$55.188	$55.19	$55.20	$55.20
Purchase #2	$43.53	3.486%	$45.0475	$45.05	$45.05	$45.00
Purchase #3	$248.86	9.656%	$272.8899	$272.89	$272.90	$272.90
Purchase #4	$68.94	13.345%	$78.14	$78.14	$78.15	$78.10
Purchase #5	$82.75	6.521%	$88.1461	$88.15	$88.15	$88.10
Purchase #6	$150.56	12.610%	$169.5456	$169.55	$169.55	$169.50
Purchase #7	$95.43	7.368%	$102.4613	$102.46	$102.45	$102.50
7 purchase totals =	$742.57		$811.4184	$811.43	$811.45	$811.30