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	$216.60	13.372%	$245.5638	$245.56	$245.55	$245.60
Purchase #2	$115.42	9.275%	$126.1252	$126.13	$126.15	$126.10
Purchase #3	$33.92	9.569%	$37.1658	$37.17	$37.15	$37.20
Purchase #4	$187.81	13.338%	$212.8601	$212.86	$212.85	$212.90
Purchase #5	$125.47	11.830%	$140.3131	$140.31	$140.30	$140.30
Purchase #6	$82.83	6.752%	$88.4227	$88.42	$88.40	$88.40
Purchase #7	$33.42	11.443%	$37.2443	$37.24	$37.25	$37.20
7 purchase totals =	$795.47		$887.6950	$887.69	$887.65	$887.70