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	$189.94	3.416%	$196.4284	$196.43	$196.45	$196.40
Purchase #2	$226.82	9.622%	$248.6446	$248.64	$248.65	$248.60
Purchase #3	$59.34	10.272%	$65.4354	$65.44	$65.45	$65.40
Purchase #4	$104.84	9.314%	$114.6048	$114.60	$114.60	$114.60
Purchase #5	$250.90	9.542%	$274.8409	$274.84	$274.85	$274.80
Purchase #6	$141.83	7.526%	$152.5041	$152.50	$152.50	$152.50
Purchase #7	$147.58	9.446%	$161.5204	$161.52	$161.50	$161.50
7 purchase totals =	$1,121.25		$1,213.9786	$1,213.97	$1,214.00	$1,213.80