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	$132.50	13.631%	$150.5611	$150.56	$150.55	$150.60
Purchase #2	$95.96	3.725%	$99.5345	$99.53	$99.55	$99.50
Purchase #3	$165.59	9.656%	$181.5794	$181.58	$181.60	$181.60
Purchase #4	$54.53	7.536%	$58.6394	$58.64	$58.65	$58.60
Purchase #5	$91.29	12.753%	$102.9322	$102.93	$102.95	$102.90
Purchase #6	$94.96	9.238%	$103.7324	$103.73	$103.75	$103.70
Purchase #7	$249.84	11.473%	$278.5041	$278.50	$278.50	$278.50
7 purchase totals =	$884.67		$975.4831	$975.47	$975.55	$975.40