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	$236.60	3.650%	$245.2359	$245.24	$245.25	$245.20
Purchase #2	$45.86	7.269%	$49.1936	$49.19	$49.20	$49.20
Purchase #3	$141.39	12.109%	$158.5109	$158.51	$158.50	$158.50
Purchase #4	$95.28	8.218%	$103.1101	$103.11	$103.10	$103.10
Purchase #5	$165.61	10.696%	$183.3236	$183.32	$183.30	$183.30
Purchase #6	$68.94	10.817%	$76.3972	$76.40	$76.40	$76.40
Purchase #7	$134.83	11.866%	$150.8289	$150.83	$150.85	$150.80
7 purchase totals =	$888.51		$966.6002	$966.60	$966.60	$966.50