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	$125.60	3.735%	$130.2912	$130.29	$130.30	$130.30
Purchase #2	$40.59	6.536%	$43.243	$43.24	$43.25	$43.20
Purchase #3	$88.61	8.277%	$95.9442	$95.94	$95.95	$95.90
Purchase #4	$144.86	13.492%	$164.4045	$164.40	$164.40	$164.40
Purchase #5	$169.37	9.817%	$185.9971	$186.00	$186.00	$186.00
Purchase #6	$162.32	9.848%	$178.3053	$178.31	$178.30	$178.30
Purchase #7	$119.69	3.230%	$123.556	$123.56	$123.55	$123.60
7 purchase totals =	$851.04		$921.7413	$921.74	$921.75	$921.70